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The relationship between total solar irradiance (TSI) forcing and summer extreme precipitation and flood frequency over western Europe is investigated from a synoptic‐scale perspective, with a focus on the role of Rossby wave packets (RWPs). Utilizing observational, model, and proxy data, we reveal a significant increase in RWP frequency along a zonal band centered around 50°N, extending from North America to western Europe, during periods of low TSI. This anomaly in RWP frequency is consistent with a significant increase in the frequency of extreme precipitation events recorded over western Europe. Sensitivity experiments conducted with a state‐of‐the‐art chemistry‐climate model corroborate our findings based on observational data. Additionally, a flood record from western Europe demonstrates a significant increase in flood frequency during low TSI years, a relationship that persists across timescales. We argue that the frequency patterns associated with TSI forcing presented in this study are robust and, therefore, valuable for estimating the frequency of extreme precipitation events over western Europe under various solar irradiance scenarios. Moreover, our findings indicate that the North Atlantic sector is more responsive to changes in solar forcing during the boreal summer than previously thought, with this effect manifesting primarily on synoptic timescales rather than the long‐term climatological mean. Plain Language Summary: The total solar irradiance change has a significant impact on precipitation extremes over western Europe. Based on statistical analysis of observed and reconstructed data, we show that during low total solar irradiance years the frequency of extreme precipitation and floods over western Europe is significantly higher than the climatology due to more frequent synoptic‐scale Rossby wave packet (RWP) events. Analysis of paleoclimate data reveals similar relationships between total solar irradiance forcing and RWP and extreme precipitation frequency for different timescales. We argue that the RWP patterns presented here are useful to estimate the evolution of extreme precipitation and floods over western Europe during the next decades/centuries under different solar irradiance scenarios. Key Points: Low solar irradiance is associated with more frequent Rossby wave packets and extreme precipitation over western Europe during summer.Paleoclimate data suggests that these links are robust across different timescales.In the scenario of decreasing solar irradiance during next decades/centuries, an increase in Sun‐related precipitation extremes is expected. [ABSTRACT FROM AUTHOR]

We address the hypothetical question of whether an increasing total solar irradiance (TSI) trend, without anthropogenic contributions, could be sufficient to explain the ongoing global warming. To this end, the intermediate-complexity climate model PlaSim is used. To consider the total internal variability, we present a set of ensemble simulations, with different forcing histories in TSI and CO2 concentration, that have converged sufficiently tightly to the relevant probability distributions to provide a satisfactory bound on any spurious trend possibly arising from a sampling bias; similar bounds on any other unforced contributions to ensemble mean trends are also estimated. A key point is the consideration, among the forcing histories, the steepest increasing trend in TSI that is still consistent with observations according to a recent study; thereby, we essentially revisit corresponding TSI reconstructions, more than 20 years after their last modeling-based evaluation, by improving the analysis through taking care of all possible sources of error or uncertainty and incorporating data that have become available since then. Without any change in CO2 concentration, our TSI trend (i.e., and upper bound on actual TSI trends) is found to be insufficient to produce outcomes compatible with the observational record in global mean surface temperature (GMST) with a nonnegligible probability. We formalize our statement for quantifiers of GMST trends through evaluating their distributions over the ensemble, and we speculate that the hypothesis about the exclusive role of an increasing TSI remains implausible even beyond our particular model setup. At the same time, if we consider a constant TSI, and the observational record in CO2 concentration is applied as forcing, the simulation results and the recorded GMST match well. While we currently need to leave the question of a precise attribution open, we conclude by pointing out that an attribution of the ongoing global warming to an increasing TSI alone could be made plausible only if a bias in the set of land-based instrumental temperature measurements were increasing more rapidly than commonly estimated; an assessment of the latter possibility is out of the scope of our study, as well as addressing solar forcing mechanisms beyond the effect of TSI. [ABSTRACT FROM AUTHOR]

The measurements of the Total Solar Irradiance (TSI) is a primary means to investigate solar activity and key measurement for understanding global climate change. The aperture diffraction is an error factor for the Solar Irradiance Absolute Radiometer (SIAR) on the Fengyun-3F (FY-3F) satellite. The diffraction effect correction factors can currently only be obtained by simulation, and they are obtained based on a series of approximate conditions that do not allow the accuracy of the diffraction correction results to be assessed. In this paper, we establish the diffraction effect measurement equipment based on the dark imaging technology and the theory of diffraction by Fraunhofer. The total light image and the aperture diffraction images of different angles were obtained by the CCD camera. The images were corrected by linearity, background, and continuity. Then, the diffraction effect curve of diffraction angle can be obtained. Finally, the diffraction correction factor of SIAR/FY-3F can be obtained by the accumulation of multiple apertures and combining the weighted integration of the solar spectrum. The results illustrated that the value of the diffraction correction factor of the SIAR aperture system on the FY-3F satellite is 2.85 × 10 − 3 , and the uncertainty of diffraction effect experimental measurement is 4.62%, which reduces the measurement error of the diffraction effect on the total solar irradiance to 1.32 × 10 − 4 . This result provides a technical basis for high-precision TSI measurement. [ABSTRACT FROM AUTHOR]

We address the hypothetical question of whether an increasing total solar irradiance (TSI) trend, without anthropogenic contributions, could be sufficient to explain the ongoing global warming. To this end, the intermediate-complexity climate model PlaSim is used. To consider the total internal variability, we present a set of ensemble simulations, with different forcing histories in TSI and CO2 concentration, that have converged sufficiently tightly to the relevant probability distributions to provide a satisfactory bound on any spurious trend possibly arising from a sampling bias; similar bounds on any other unforced contributions to ensemble mean trends are also estimated. A key point is the consideration, among the forcing histories, the steepest increasing trend in TSI that is still consistent with observations according to a recent study; thereby, we essentially revisit corresponding TSI reconstructions, more than 20 years after their last modeling-based evaluation, by improving the analysis through taking care of all possible sources of error or uncertainty and incorporating data that have become available since then. Without any change in CO2 concentration, our TSI trend (i.e., and upper bound on actual TSI trends) is found to be insufficient to produce outcomes compatible with the observational record in global mean surface temperature (GMST) with a nonnegligible probability. We formalize our statement for quantifiers of GMST trends through evaluating their distributions over the ensemble, and we speculate that the hypothesis about the exclusive role of an increasing TSI remains implausible even beyond our particular model setup. At the same time, if we consider a constant TSI, and the observational record in CO2 concentration is applied as forcing, the simulation results and the recorded GMST match well. While we currently need to leave the question of a precise attribution open, we conclude by pointing out that an attribution of the ongoing global warming to an increasing TSI alone could be made plausible only if a bias in the set of land-based instrumental temperature measurements were increasing more rapidly than commonly estimated; an assessment of the latter possibility is out of the scope of our study, as well as addressing solar forcing mechanisms beyond the effect of TSI.

This article acts as an introduction to the JGR‐Atmospheres special section titled Monitoring the Earth Radiation Budget and its Implication to Climate Simulations: Recent Advances and Discussions. It outlines the key findings presented in the articles published in the special section. Additionally, it delves into some of the emerging trends in the ongoing research within this field of research. Plain Language Summary: This is the introduction to the special collection "Monitoring the Earth Radiation Budget and its Implication to Climate Simulations: Recent Advances and Discussions" Key Points: Motivations for this special section are presentedPapers in this special issue are summarizedSome discussions on the current state of the solar forcing within climate simulations [ABSTRACT FROM AUTHOR]

The prediction of total solar irradiance (TSI) time series holds significant importance in the study of solar activity and the assessment of solar energy resources. The variational mode decomposition-based long short-term memory (VMD-LSTM) model is a hybrid deep learning model that demonstrates high prediction accuracy on long-term time series. To address the information leakage issue faced by hybrid models based on VMD and other data preprocessing methods, this study proposes a prediction method for hybrid deep learning models called dualfusion variational mode decomposition (DFVMD), which modifies the VMD decomposition approach. The DFVMD-LSTM model utilizes multiple TSI datasets as model features, and multisource datasets and multiple model comparison experiments are employed to verify the applicability and robustness of the model. The experimental results show that the DFVDM-LSTM model significantly reduces the periodic TSI prediction deviation introduced by the LSTM model. Furthermore, regardless of the training period or prediction horizon, the DFVMD-LSTM model exhibits an average root mean square error (RMSE) reduction of 14.79 % and an average mean absolute error (MAE) decrease of 21.50 %, demonstrating the superior predictive performance and improved reliability of the DFVDM-LSTM method. [ABSTRACT FROM AUTHOR]

Differences among total solar irradiance (TSI) estimates are most pronounced during the so‐called "ACRIM Gap" of 1989–1991, when available satellite‐based observations disagree in trend and no observations exist from satellites with on‐board calibration. Different approaches to bias‐correcting noisy satellite‐based observations lead to discrepancies of up to 0.7 W/m2 in the change in TSI during the Gap. Using a Bayesian hierarchical model for TSI (BTSI), we jointly infer TSI during the ACRIM Gap from satellite‐based observations and proxies of solar activity. In addition, BTSI yields estimates of noise and drift in satellite‐based observations and calibration for proxy records. We find that TSI across the ACRIM Gap changes by only 0.01 W/m2, with a 95% confidence interval of [−0.07, 0.09] W/m2. Our results are consistent with the PMOD CPMDF and Community Consensus TSI reconstructions and inconsistent with the 0.7 W/m2 trend reported in the ACRIM composite reconstruction. Constraints on the trend across the ACRIM Gap are primarily obtained through constraints on the drift in the Nimbus‐7 satellite that are afforded by overlapping satellite and proxy observations. Plain Language Summary: Total solar irradiance (TSI) is a measure of the solar power per unit area received by Earth from the Sun. Accurately estimating TSI, and its variations, has been a longstanding methodological challenge due to the difficulty of correcting for satellite observations of TSI, especially during periods without many overlapping observers for comparison, such as during the so‐called "ACRIM Gap" of 1989–1991 when no satellites with on‐board calibration were observing TSI. We demonstrate the effectiveness of a Bayesian statistical model in objectively correcting satellite instrument error during the ACRIM Gap by simultaneously taking in observations from both satellite instruments and indirect measures of TSI such as sunspot number. This model is the first to simultaneously correct and use direct and indirect observations to reconstruct TSI. The results of the model are consistent with some past reconstructions of TSI in finding little or no change in irradiance during the ACRIM Gap, contrary to the ACRIM composite that estimated a large increase over this period. Key Points: The change in total solar irradiance (TSI) across a gap in observations from 1989–1991 differs by up to 0.7 W/m2 between reconstructionsA Bayesian hierarchical model is used to combine satellite‐based and proxy observations and better constrain TSI across the ACRIM GapTSI is found to change by only 0.01 [95% CI −0.07, 0.09] W/m2 across the ACRIM Gap, in keeping with some previous reconstructions [ABSTRACT FROM AUTHOR]

Under the background of global warming, the frequency and intensity of extreme climate have increased, especially extreme high temperatures. In order to correctly predict the changes in the extreme high temperatures in summer in China in this century, it is urgent to deepen the understanding of the characteristics and physical mechanisms of the extreme high temperatures in summer on the centennial timescale. Many researchers have explored the mechanism of the influences of the variability of the solar cycle on climate change, while the mechanism of the influences of the centennial variation of solar activity on climate change remains elusive. Here, we use the outputs from the Control (CTRL) experiment, Total solar irradiance and Orbital (TSI_ORB) experiment, and Orbital (ORB) experiment from Nanjing Normal University-Holocene (NNU-Hol) experiments to study the extreme high temperatures in summer in China during the Holocene. On the basis of verifying the consistency of the centennial period between the TSI (TSI_ORB minus ORB plus CTRL) experiment and the reconstructed data, we compared the centennial variation characteristics of the summer extreme high temperature in the CTRL experiment and the TSI experiment. It shows that under the modulation of total solar irradiance, the centennial spatial pattern of the summer extreme high temperatures changed from dipole mode to uniform mode, with 300-year and 500-year periodicity, compared to the influence of only internal variability. On the centennial time scale, the greatest difference is located in northeast China. The subsidence movement and the reduction of cloud cover caused by the anticyclone under the control of high-pressure lead to the increase of downward solar radiation, thus making a positive center is showed in northeast China on the impacts of total solar irradiance. Furthermore, the center of the Rossby wave train in the barotropic structure of the upper circulation related to the summer extreme high temperature significantly moves northward. This barotropic structure is composed of continuous pressure ridges from Eurasia to North America and the North Atlantic, which is conducive to the increase of the summer extreme high temperatures. Furthermore, we investigated the underlying physical mechanisms. Under the influence of total solar irradiance, the Pacific Decadal Oscillation (PDO) with the same centennial cycle as extreme high temperatures lead to obvious subsidence movement and increase of radiation flux, causing an increase in extreme high temperatures over northeast China. [ABSTRACT FROM AUTHOR]

A tree‐ring stable oxygen isotope (δ18O) chronology was developed for the past 171 years by four Abies pindrow trees growing in southwest foothills of High Asia, northern Pakistan, which is correlated with observed and modelled δ18O of precipitation in Islamabad over the instrumental period. The averaged tree‐ring δ18O chronology is significantly negative correlated with local (r = −.651, p <.001, n = 38) and regional (r = −.664, p <.001, n = 65) summer precipitation variations. Analysis of vertically integrated water vapour flux and surface wind field suggests that the sampling site is located at the northern limit of the Indian summer monsoon (ISM). Our tree‐ring δ18O series is significantly (p <.001, n = 143) negatively correlated with observed Homogenous India rainfall, All Indian rainfall, Core‐Monsoon India rainfall and Northwest India rainfall. This is the first detected ISM signal from tree‐ring δ18O over northern Pakistan. Several ISM‐related paleoclimate proxies, including three stalagmites δ18O series (Sahiya cave, Jhumar cave and Qunf cave) and a tree‐ring δ18O series (Manali), show consistent variability and a correlation coefficient of.566 (p <.001, n = 165) with our tree‐ring δ18O, suggesting that a combination of multiple proxies may be potentially useful to understand the full perspective of ISM before instrumental era. In addition, we found that the satellite‐observed winter Total Solar Irradiance exerts influence on the tree‐ring δ18O variation (r =.643, p <.001, n = 38), which may be linked to runoff of the Indus River and ISM precipitation. [ABSTRACT FROM AUTHOR]

Total solar irradiance (TSI) data play an important role in guiding production, but they are difficult to predict accurately because of nonlinearity and noise. In this paper, a hybrid model of complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) and a bidirectional gated recurrent units network (BiGRU) that introduces an attention mechanism into adaptive noise is proposed. First, the CEEMDAN method is used to decompose the TSI. Then, the fuzzy entropy (FE) of each component is calculated, and the input sequence is synthesized by K-means clustering of the near waves. Finally, the combined sequences are trained in a BiGRU model with multiple hidden layers, and the attention mechanism acts on the time step. In this paper, the TSI at 5485 time points was predicted with MAE, MSE and MAPE values of 0.1122, 0.0259, and 0.00008, respectively. Compared with BiGRU, the hybrid model decreased by 11.74% on MAE, 5.29% on MSE and 0.009% on MAPRE. The CEEMDAN-BiGRU-Attention model has good application prospects in the field of TSI prediction. [ABSTRACT FROM AUTHOR]

Under the background of global warming, the frequency and intensity of extreme climate have increased, especially extreme high temperatures. In order to correctly predict the changes in the extreme high temperatures in summer in China in this century, it is urgent to deepen the understanding of the characteristics and physical mechanisms of the extreme high temperatures in summer on the centennial timescale. Many researchers have explored the mechanism of the influences of the variability of the solar cycle on climate change, while the mechanism of the influences of the centennial variation of solar activity on climate change remains elusive. Here, we use the outputs from the Control (CTRL) experiment, Total solar irradiance and Orbital (TSI_ORB) experiment, and Orbital (ORB) experiment from Nanjing Normal University-Holocene (NNU-Hol) experiments to study the extreme high temperatures in summer in China during the Holocene. On the basis of verifying the consistency of the centennial period between the TSI (TSI_ORB minus ORB plus CTRL) experiment and the reconstructed data, we compared the centennial variation characteristics of the summer extreme high temperature in the CTRL experiment and the TSI experiment. It shows that under the modulation of total solar irradiance, the centennial spatial pattern of the summer extreme high temperatures changed from dipole mode to uniform mode, with 300-year and 500-year periodicity, compared to the influence of only internal variability. On the centennial time scale, the greatest difference is located in northeast China. The subsidence movement and the reduction of cloud cover caused by the anticyclone under the control of high-pressure lead to the increase of downward solar radiation, thus making a positive center is showed in northeast China on the impacts of total solar irradiance. Furthermore, the center of the Rossby wave train in the barotropic structure of the upper circulation related to the summer extreme high temperature significantly moves northward. This barotropic structure is composed of continuous pressure ridges from Eurasia to North America and the North Atlantic, which is conducive to the increase of the summer extreme high temperatures. Furthermore, we investigated the underlying physical mechanisms. Under the influence of total solar irradiance, the Pacific Decadal Oscillation (PDO) with the same centennial cycle as extreme high temperatures lead to obvious subsidence movement and increase of radiation flux, causing an increase in extreme high temperatures over northeast China.

Since the late 1970s, successive satellite missions have been monitoring the sun's activity and recording the total solar irradiance (TSI). Some of these measurements have lasted for more than a decade. In order to obtain a seamless record whose duration exceeds that of the individual instruments, the time series have to be merged. Climate models can be better validated using such long TSI time series which can also help to provide stronger constraints on past climate reconstructions (e.g., back to the Maunder minimum). We propose a 3‐step method based on data fusion, including a stochastic noise model to take into account short and long‐term correlations. Compared with previous products scaled at the nominal TSI value of ∼1361 W/m2, the difference is below 0.2 W/m2 in terms of solar minima. Next, we model the frequency spectrum of this 41‐year TSI composite time series with a Generalized Gauss‐Markov model to help describe an observed flattening at high frequencies. It allows us to fit a linear trend into these TSI time series by joint inversion with the stochastic noise model via a maximum‐likelihood estimator. Our results show that the amplitude of such trend is ∼−0.004 ± 0.004 W/(m2yr) for the period 1980–2021. These results are compared with the difference of irradiance values estimated from two consecutive solar minima. We conclude that the trend in these composite time series is mostly an artifact due to the colored noise. Key Points: Application of data fusion to merge 41 years of satellite observations into a composite total solar irradiance time seriesA comprehensive time‐frequency analysis to characterize the solar cycle and the stochastic noiseInvestigation of variations at solar minima to distinguish between stochastic noise and underlying phenomena linked to the solar activity [ABSTRACT FROM AUTHOR]

• Strong linkage between rock magnetic parameters and the instrumental rainfall data. • The cyclic variation of rainfall during the past 2100 years. • The strong coherence between rock magnetic data and Total Solar Irradiance (TSI). • Similarities with other paleoclimatic records in the region and teleconnection between different climatic systems. The present study is aimed at understanding the sub-decadal to decadal scale variability of rainfall in southern India based on a sedimentary record (dated using AMS 14C, 210Pb, 137Cs methods) from Madagadakere lake (MK) situated in the foothills of the Western Ghats. A strong linkage between sediment magnetic signature and the instrumental rainfall record for the past 115 years demonstrates that the environmental magnetic proxies are useful and have greater applicability in the paleomonsoonal reconstructions. Fluctuations in the mineral magnetic, grain size, and geochemical parameters of the studied sediment profile revealed that pedogenic activity and terrigenous sediment flux to the lake varied cyclically during the Late Holocene period in response to varying intensities of rainfall. The region experienced higher or increasing trend of rainfall during periods 2100–1900, 1600–1250, 1050–925, 680–600, and 350–270 cal. years B.P., with low rainfall/decreasing trend during intervening periods. The spectral analysis of magnetic parameters revealed significant periodicities of 291, 164, 101, 54, 48, 44, 41, 39, 105, 48, and 41 years, which are very well documented in other paleoclimatic records, and whose origin is ascribed unequivocally to variation in Total Solar Irradiance (TSI). We propose that the periods of higher values for concentration-dependent magnetic parameters (higher rainfall) can be attributed to the timings of the increased TSI, positive mode of Indian Ocean Dipole (IOD), northward migration of Intertropical convergence zone (ITCZ) and weakened El-Niño southern oscillation (ENSO) activity in the region, establishing the teleconnection between different climatic systems. [ABSTRACT FROM AUTHOR]

The Solar Radiation and Climate Experiment (SORCE) was a NASA mission that operated from 2003 to 2020 to provide key climate-monitoring measurements of total solar irradiance (TSI) and solar spectral irradiance (SSI). This 17-year mission made TSI and SSI observations during the declining phase of Solar Cycle 23, during all of Solar Cycle 24, and at the very beginning of Solar Cycle 25. The SORCE solar-variability results include comparisons of the solar irradiance observed during Solar Cycles 23 and 24 and the solar-cycle minima levels in 2008 – 2009 and 2019 – 2020. The differences between these two minima are very small and are not significantly above the estimate of instrument stability over the 11-year period. There are differences in the SSI variability for Solar Cycles 23 and 24, notably for wavelengths longer than 250 nm. Consistency comparisons with SORCE variability on solar-rotation timescales and solar-irradiance model predictions suggest that the SORCE Solar Cycle 24 SSI results might be more accurate than the SORCE Solar Cycle 23 results. The SORCE solar-variability results have been useful for many Sun–climate studies and will continue to serve as a reference for comparisons with future missions studying solar variability. [ABSTRACT FROM AUTHOR]

The Solar Radiation and Climate Experiment (SORCE) was a NASA mission that operated from 2003 to 2020 to provide key climate-monitoring measurements of total solar irradiance (TSI) and solar spectral irradiance (SSI). This topical collection provides an overview of some of the key SORCE science results, an overview of mission operations and how anomalies impacted the science observations, a detailed description of the updated algorithms used in producing the final data products of TSI and SSI from the four SORCE instruments, and results from an underflight calibration-rocket experiment flown in June 2018. The 17-year-long SORCE mission has made many contributions to the climate records of TSI and SSI that date back to the 1970s, and, fortunately, similar observations from the Total and Spectral Solar Irradiance Sensor (TSIS-1) are able to continue these Sun-climate records after SORCE without a gap. [ABSTRACT FROM AUTHOR]

As an important indicator of solar activity, the long‐term total solar irradiance (TSI) observations are needed to uncover the impact of solar activity on Earth's climate. In this paper, the periodic variation of TSI and its relationships with sunspot number and Ca II K index are analyzed by using the satellite observation data from 1979 to 2015 and the wavelet method. The results of continuous wavelet analysis show that TSI, sunspot number and Ca II K index all have significant and stable oscillation periods of 9∼13 years and intermittent oscillation periods of 2∼6 months only during the time of intense solar activity. Moreover, the results of cross wavelet analysis indicate that the effect of sunspot number and Ca II K index on TSI is mainly reflected in the period of 9∼13 years with one month phase lag, and sunspot number and Ca II K index cannot explain the TSI variation in the period of 3∼6 months. Under the condition of considering the phase relationship and the model order, the TSI reconstruction model is established and the monthly TSI time series from 1907 to 1978 is restored. Key Points: Sunspot number and Ca II K index all have significant oscillation periods of 9∼13 years and intermittent oscillation periods of 2∼6 monthsThe effect of sunspot number and Ca II K index on total solar irradiance (TSI) is mainly reflected in the period of 9∼13 years with one month phase lagThe TSI reconstruction model is established with considering the phase relationship [ABSTRACT FROM AUTHOR]

Abstract As an important indicator of solar activity, the long‐term total solar irradiance (TSI) observations are needed to uncover the impact of solar activity on Earth's climate. In this paper, the periodic variation of TSI and its relationships with sunspot number and Ca II K index are analyzed by using the satellite observation data from 1979 to 2015 and the wavelet method. The results of continuous wavelet analysis show that TSI, sunspot number and Ca II K index all have significant and stable oscillation periods of 9∼13 years and intermittent oscillation periods of 2∼6 months only during the time of intense solar activity. Moreover, the results of cross wavelet analysis indicate that the effect of sunspot number and Ca II K index on TSI is mainly reflected in the period of 9∼13 years with one month phase lag, and sunspot number and Ca II K index cannot explain the TSI variation in the period of 3∼6 months. Under the condition of considering the phase relationship and the model order, the TSI reconstruction model is established and the monthly TSI time series from 1907 to 1978 is restored.

The Solar Radiation and Climate Experiment (SORCE) was a NASA mission that operated from 2003 to 2020 to provide key climate-monitoring measurements of total solar irradiance (TSI) and solar spectral irradiance (SSI). Three important accomplishments of the SORCE mission are i) the continuation of the 42-year-long TSI climate data record, ii) the continuation of the ultraviolet SSI record, and iii) the initiation of the near-ultraviolet, visible, and near-infrared SSI records. All of the SORCE instruments functioned well over the 17-year mission, which far exceeded its five-year prime mission goal. The SORCE spacecraft, having mostly redundant subsystems, was also robust over the mission. The end of the SORCE mission was a planned passivation of the spacecraft following a successful two-year overlap with the NASA Total and Spectral Solar Irradiance Sensor (TSIS) mission, which continues the TSI and SSI climate records. There were a couple of instrument anomalies and a few spacecraft anomalies during SORCE's long mission, but operational changes and updates to flight software enabled SORCE to remain productive to the end of its mission. The most challenging of the anomalies was the degradation of the battery capacity that began to impact operations in 2009 and was the cause for the largest SORCE data gap (August 2013 – February 2014). An overview of the SORCE mission is provided with a couple of science highlights and a discussion of flight anomalies that impacted the solar observations. Companion articles about the SORCE instruments and their final science data-processing algorithms provide additional details about the instrument measurements over the duration of the mission. [ABSTRACT FROM AUTHOR]

Abstract The Earth system responds to solar variability on a wide range of timescales. Knowledge of total solar irradiance (TSI) and solar spectral irradiance (SSI) spanning minutes to centuries is needed by scientists studying a broad array of research applications. For these purposes, the NOAA National Centers for Environmental Information (NCEI) Climate Data Record Program established the Solar Irradiance Climate Data Record. Version 2 of the Naval Research Laboratory's solar variability models that are derived from and demonstrate consistency with irradiance observations specifies TSI and SSI for the Solar Irradiance Climate Data Record. We establish the veracity of the Naval Research Laboratory models on the timescales and over the wavelength range for which the Sun is known to vary and, thereby, specify the utility of these models. Through comparisons with irradiance observations and independent models, we validate NRLTSI2 estimates of TSI on solar rotational (~27‐day), solar cycle (~11‐year), and multidecadal (spacecraft era) variability timescales. Similarly, we validate NRLSSI2 estimates of SSI rotational variability in the ultraviolet through the mid‐visible spectrum. Validation of NRLSSI2 estimates at longer wavelengths, particularly in the near‐infrared, and for the full spectrum at solar cycle timescales and longer is not possible with the current observational record due to instrumental noise and instrument instability. We identify where key new data sets, such as observations from the Total and Spectral Solar Irradiance Sensor‐1, are expected to provide a fuller understanding of total and spectral solar irradiance variability on multiple timescales.

Absolute radiometers are based on electrical substitution radiometers, which compare optical and electrical power. The same physical principle applies to standard reference detectors operating at cryogenic temperatures and room temperature radiometers for total solar irradiance (TSI) measurements. Both types rely on the cavity with an internal low-reflectance coating to absorb incident radiation similar to a black body. The cavity shape design requires an analysis of the coating reflection properties. Like many materials, ultra-black Ni-P exhibits a mixture of diffuse and specular reflection that depends on the angle of incidence of light in the pores. We employed ray-tracing software to study the impact of the geometry on the absorptivity and distribution of the scattered rays. We describe the scattering model of the black coating in terms of the bidirectional reflectance distribution function. Also, we examined the difficulties of Ni-P electroless deposition and blackening inside the cavity. The measured absorptance of the cavity showed some discrepancies of the simulated absorptance mostly probably due to Ni-P non-uniformity coating.

The study presents the results of the correlation analysis for the average seasonal values of intensity of solar UV radiation (297–330 nm), as well as for the energy of the lines of solar spectral irradiance with total solar irradiance and total magnetic field of the Sun for the period of 2008–2018 (the 24th cycle of solar activity). The analysis is carried out using the spectral observations of solar UV radiation at Novolazarevskaya station (Antarctica), the SORCE spacecraft and WSO (Wilcox Solar Observatory) data. The dependence of the UVB-UVA radiation of 280–315 nm (UV-B) and 315–400 nm (UV-A) on changes in the total magnetic field of the Sun is revealed. [ABSTRACT FROM AUTHOR]

The Joint Total Solar Irradiance Monitor (JTSIM) is due to fly onboard the Fengyun-3E spacecraft and aims to measure the Total Solar Irradiance (TSI) in orbit. The instruments on the Fengyun-3E/JTSIM include the Digital Absolute Radiometer (DARA) from the Physikalisch Meteorologisches Observatorium, Davos and World Radiation Center (PMOD/WRC) and the Solar Irradiance Absolute Radiometer (SIAR) from the Changchun Institute of Optics, Fine Mechanics and Physics Chinese Academy of Sciences (CIOMP/CAS). Radiometers from Switzerland and China will monitor the TSI variability on the same pointing system for eight years. The scientific data from JTSIM will support the analysis of potential long-term trends in the Sun's variability. In this article, we describe the sensor box and the electronics box of JTSIM, the measurement principle, and the operation mode of SIAR. Before launch, we accomplished some primary calibrations of SIAR in the CIOMP laboratory, including the aperture area, cavity absorption, non-equivalence, diffraction, etc. Other parameters will be calibrated on orbit. The combined uncertainty of SIAR for characterization is 231 – 233 ppm depending on the measurement channel. The characterization of SIAR is an International System of Units (SI)-native scale calibration. An end-to-end calibration against the World Radiometric Reference (WRR) standard or the Total Irradiance Radiometer Facility (TRF) is a procedure where SIAR is directly calibrated with the WRR reference radiometers. The WRR factor for SIAR is 0.99939 – 1.00092 and the combined measurement uncertainty is 0.074% – 0.099%, depending on the measurement channel. [ABSTRACT FROM AUTHOR]

The correlation between the averaged reconstructed March temperature record for Kyoto, Japan, and the reconstructed Total Solar Irradiance (TSI) over 660 years from 1230 to 1890 gives evidence with 98% probability that the Little Ice Age with four cold periods is forced by variations of TSI. If the correlation is restricted to the period 1650-1890, with two cold periods in the 17th and 19th century and for which two independent reconstructed March temperature records are available, the probability of solar forcing increases to 99.99%. As solar irradiance variations have a global effect there has to be a global climatic solar forcing impact. However, by how much global temperature were lower during these minima and with what amplitude TSI was varying is not accurately known. The two quantities, global temperature and TSI, are linked by the energy equilibrium equation for the Earth system. The derivation of this equation with respect to a variation of the solar irradiance has two terms: A direct forcing term, which can be derived analytically and quantified accurately from the Stefan-Boltzmann law, and a second term, describing indirect influences on the surface temperature. If a small TSI variation should force a large temperature variation, then it has to be the second indirect term that strongly amplifies the effect of the direct forcing. The current knowledge is summarized by three statements: -During the minima periods in the 13th, 15/16th, 17th, and 19th centuries the terrestrial climate was colder by 0.5-1.5 °C; -Indirect Top-down and Bottom-up mechanisms do not amplify direct forcing by a large amount, i.e. indirect solar forcing is of the same magnitude (or smaller) as direct solar forcing; -The radiative output of the Sun cannot be lower by more than 2 Wm~2 below the measured present-day TSI value during solar cycle minimum. These three statements contradict each other and it is concluded that at least one is not correct. Which one is a wrong statement is presently not known conclusively. It is argued that it is the third statement and it is speculated that over centennial time scales the Sun might vary its radiance significantly more than observed so far during the last 40 years of space TSI measurements. To produce Maunder minimum type cold climate excursions, a TSI decrease of the order of 10 Wm~2 is advocated. [ABSTRACT FROM AUTHOR]

Total Solar Irradiance (TSI) quantifies the solar energy received by the Earth and therefore is of direct relevance for a possible solar influence on climate change on Earth. We analyse the TSI space measurements from 1991 to 2021, and we derive a regression model that reproduces the measured daily TSI variations with a Root Mean Square Error (RMSE) of 0.17 W/m2. The daily TSI regression model uses the MgII core to wing ratio as a facular brightening proxy and the Photometric Sunspot Index (PSI) as a measure of sunspot darkening. We reconstruct the annual mean TSI backwards to 1700 based on the Sunspot Number (SN), calibrated on the space measurements with an RMSE of 0.086 W/m2. The analysis of the 11 year running mean TSI reconstruction confirms the existence of a 105 year Gleissberg cycle. The TSI level of the current grand minimum is only about 0.15 W/m2 higher than the TSI level of the grand minimum in the beginning of the 18th century.

The solar energy received by the atmosphere of the Earth is universally distributed, which constitutes the atmospheric dynamics. The changes observed in the climate of the Earth are due to solar output variations. Some detailed reviews have accounted for the influence of solar activities on the climate using sunspot number derived from peak Sun hours, but has gaps in analyzing critical statistical background information, seasonal, latitudinal and solar activity year validation. A number of statistical concepts are explained in order to enhance our scientific knowledge of climate response to solar activity variation. The influence of geomagnetism to climate response is also examined. This review will serve as analysis and research methodology discourse which could be an application of scientific method. Additionally, this review discusses the influence of the solar activity on climate change based on the existing literature, by focusing on solar activities other than sunspot number alone. Here, we also validate methods using forward and inverse modeling, mean percentage difference, and relative variability. Results indicated that the total solar irradiance (TSI) has remained the main focus of Sun-climate interaction with somewhat negligent on energetic particle precipitation resulting from geomagnetic disturbance reaching the atmosphere. However, statistical concept remains asset to investigate the solar activity influence on climate in both local and global latitudes. We therefore recommend provision of solar quantities data to researchers for further study. [ABSTRACT FROM AUTHOR]

Neutron monitor counting rates and solar wind velocity, interplanetary magnetic field, sunspot number and total solar irradiance measurements from 2013 to 2018 corresponding to the end of solar maximum and the decreasing phase of the Solar Cycle 24 have been used. The main objective is to check whether the periodicities observed in the cosmic rays are affected by the magnetic rigidity or the height at which the neutron monitors are placed. A Global Neutron Monitor (GNM) has been defined as representative of the neutron monitor global network. This GNM is constructed by averaging the counting rates of a set of selected neutron monitors. The selection process is based on the combination of three new data quality criteria, which are applied to neutron monitors in the Neutron Monitor Data Base giving a final pool of 22 selected neutron monitors. Morlet wavelet analysis is applied to the GNM and the selected solar activity parameters to find the common periodicities. Short-term periodicities of 13.5, 27, 48, 92, 132 and 298 days have been observed in cosmic ray intensity. A clear inverse relationship between rigidity and spectral power has been obtained for the 13.5-, 48-, 92-, 132-day periods. A not so clear but still observed direct relationship between the height of the neutron monitors and the spectral power for the 48-, 92-, 132-day periods has been also found. The periodicity of 92 days is the one which shows the highest dependence with rigidity cutoff and height. As far as we know, this is the first time that these dependencies are reported. We think that these observations could be explained by assuming some cosmic ray intensity energy dependence in such periodicities and a competitive effect between rigidity and height. [ABSTRACT FROM AUTHOR]

The Total Solar Irradiance (TSI) primarily varies on an 11-year time scale and is governed by features such as sunspots and associated decay products such as plage and faculae. These short-lived physical features can also modulate the solar irradiance at intermediate and short temporal scales. Here we investigate the periodic variations, at solar-surface-rotation time scales, of photometric indices derived from images obtained at the San Fernando Observatory (SFO), and we compare them to the properties of the contemporaneous TSI as measured by the Total Irradiance Monitor (TIM) onboard the SOlar Radiation and Climate Experiment (SORCE) spacecraft. Both the daily ground- and space-based data, which span from early 2003 to late 2018, present missing pixels. We use an autoregressive gap-filling method to construct continuous time series to be analyzed via Fourier and wavelet spectral techniques. Lomb–Scargle periodograms, which can handle time series with missing data, are used for comparison. Both the Fourier spectral power and the periodograms yield compatible results with statistically significant periodicities in the range 25 – 35 days. All of the time series have maximum power at 27 days. Significant secondary periods are found at 29 – 30 days and 34 – 35 days. Wavelet analyses of the full time series show that the photometric index resulting from the red-continuum photometric sum [ Σ r ] and the TSI exhibit common high power at surface-solar-rotation scales during the active part of the solar cycle. The phase relation at the surface-solar-rotation scales is not definite. During the solar minimum interval between Solar Cycles (SCs) 23 and 24, variations in the TSI are found to be related to variations both in the photometric index Σ K , calculated from Ca ii K-line photometric sums and in the magnetic flux in the solar activity latitudinal band (as found in previous work). This suggests that the TSI changes during the minimum are caused by the reduced line-blanketing effect of diffused magnetic field. [ABSTRACT FROM AUTHOR]

The solar variations, solar–climate interactions, and the mechanisms controlling the response of Earth’s climate system are important to understand the effect of solar variability on climate change. The solar magnetic field is directly/indirectly disturbing the interplanetary space, the ionosphere, the magnetosphere, and even the atmosphere. To investigate the contribution of varying galactic cosmic flux, the role of sunspot number (Rz), galactic cosmic ray (GCR) rates, cloud condensation nuclei (CCN), total solar irradiance (TSI), CO 2 concentration and the global surface temperature (GST) is examined. The variations of TSI can partially explain the global increase in temperature, and it accounts for about 0. 5 ∘ C warming experienced from 1950 to 2016. Therefore, the future predictions of global warming should take into account the effects due to long-term changes in the galactic CRs, the low-level cloud condensation (LLC), etc. The concentrations of CO 2 increased in the upper atmosphere by 19% during the last 65 years. A strong correlation between LLC and GST suggests a linear relationship between these parameters. These observations are suggestive of the possible role of GCRs in global climate. [ABSTRACT FROM AUTHOR]

The effects of total solar irradiance (TSI) and volcanic activity on long-term global temperature variations during solar cycles 19–23 were studied. It was shown that a large proportion of climate variations can be explained by the mechanism of action of TSI and cosmic rays (CRs) on the state of the lower atmosphere and other meteorological parameters. The role of volcanic signals in the 11-year variations of the Earth's climate can be expressed as several years of global temperature drop. Conversely, it was shown that the effects of solar, geophysical, and human activity on climate change interact. It was concluded that more detailed investigations of these very complicated relationships are required, in order to be able to understand issues that affect ecosystems on a global scale.

Solar radiation is a forcing of the climate system with a quasi-11-year period. As a quasi-period forcing, the influence of the phase of the solar cycle on the ocean system is an interesting topic of study. In this paper, the authors investigate a particular feature, the ocean heat content (OHC) anomaly, in different phases of the total solar irradiance (TSI) cycle. The results show that almost opposite spatial patterns appear in the tropical Pacific during the ascending and declining phases of the TSI cycle. Further analysis reveals the presence of the quasi-decadal (~11-year) solar signal in the SST, OHC and surface zonal wind anomaly field over the tropical Pacific with a high level of statistical confidence (>95%). It is noted that the maximum centers of the ocean temperature anomaly are trapped in the upper ocean above the main pycnocline, in which the variations of OHC are related closely with zonal wind and ocean currents.

The Earth system responds to solar variability on a wide range of timescales. Knowledge of total solar irradiance (TSI) and solar spectral irradiance (SSI) spanning minutes to centuries is needed by scientists studying a broad array of research applications. For these purposes, the NOAA National Centers for Environmental Information (NCEI) Climate Data Record Program established the Solar Irradiance Climate Data Record. Version 2 of the Naval Research Laboratory's solar variability models that are derived from and demonstrate consistency with irradiance observations specifies TSI and SSI for the Solar Irradiance Climate Data Record. We establish the veracity of the Naval Research Laboratory models on the timescales and over the wavelength range for which the Sun is known to vary and, thereby, specify the utility of these models. Through comparisons with irradiance observations and independent models, we validate NRLTSI2 estimates of TSI on solar rotational (~27‐day), solar cycle (~11‐year), and multidecadal (spacecraft era) variability timescales. Similarly, we validate NRLSSI2 estimates of SSI rotational variability in the ultraviolet through the mid‐visible spectrum. Validation of NRLSSI2 estimates at longer wavelengths, particularly in the near‐infrared, and for the full spectrum at solar cycle timescales and longer is not possible with the current observational record due to instrumental noise and instrument instability. We identify where key new data sets, such as observations from the Total and Spectral Solar Irradiance Sensor‐1, are expected to provide a fuller understanding of total and spectral solar irradiance variability on multiple timescales. Plain Language Summary: An understanding of total and spectral solar irradiance is essential for Earth atmospheric and climate studies because the Sun's energy incident at the top of Earth's atmosphere is the dominant energy source driving a myriad of interactions that establish Earth's climate. We describe how the National Oceanographic and Atmospheric Administration's Solar Irradiance Climate Data Record is meeting the goal to model variability in the Sun's irradiance, identify limitations in our current understanding of solar irradiance variability on multiple timescales and over a broad spectral range, and highlight where new observations are expected to provide a fuller understanding. Key Points: The Naval Research Laboratory's solar variability models, NRLTSI2 and NRLSSI2, establish the Solar Irradiance Climate Data Record (CDR)The CDR total and spectral (between 265 and 500 nm) solar rotational estimates are validated by observations on 27‐day solar rotationsOn solar cycle timescales and longer, particularly in the spectrum, differences in observational data sets preclude model validation [ABSTRACT FROM AUTHOR]

Solar radiation pressure is the main driving force and error source for precision orbit determination of navigation satellites. It is proportional to the solar irradiance,which is the"sun constant". In regular calculation,the"solar constant"is regard as a constant. However,due to the existence of sunspots,flares,etc.,the solar constant is not fixed,the change in the year is about 1%. To investigate the variation of solar irradiance,we use interpolation and average segment modeling of total solar irradiance data of SORCE,establishing variance solar radiation pressure(VARSRP)model and average solar radiation pressure(AVESRP)model based on the built solar pressure model(SRPM)(constant model). According to observation data of global positioning system(GPS)and Beidou system(BDS)in 2015 and comparing the solar pressure acceleration of VARSRP,AVESRP and SRPM,the magnitude of change can reach 10-10 m/s~2. In addition,according to the satellite precise orbit determination,for GPS satellites,the results of VARSRP and AVESRP are slightly smaller than those of the SRPM model,and the improvement is between 0.1 to 0.5 mm. For geosynchronous orbit(GEO)satellites of BDS,The AVESRP and VARSRP have an improvement of 3.5 mm and 4.0 mm,respectively,based on overlapping arc,and SLR check results show the AVESRP model and the VARSRP model is improved by 2.3 mm and 3.5 mm,respectively. Moreover,the change of inclined geosynchronous orbit(IGSO)satellites and medium earth orbit(MEO)satellites is relatively small,and the improvement is smaller than 0.5 mm. [ABSTRACT FROM AUTHOR]

We used a thermodynamic climate model to compute the Northern Hemisphere temperature anomaly for the period 1980–2500. We obtained temperature anomalies for the ocean, the combined ocean-land area and the land. Two IPCC et al. (2007) CO 2 concentration scenarios were considered, the high RCP8.5 and the low RCP4.5, we also included two estimates of the Total Solar Irradiance (TSI). We found that in the RCP8.5 scenario the effect of the TSI is to prevent the temperature for having a runaway behavior after the year 2240, that otherwise it would have due to the high CO 2 emission; it is the TSI that makes the temperature anomalies to have an inflection and start decreasing. For the RCP4.5 scenario, without the solar effect, the temperature anomaly after 2075 presents an inflection and becomes constant after the year 2120, but the temperature anomaly has a clear decreasing trend when including the TSI. The TSI presents three future secular minima in the studied period. They introduce only perturbations on the general decreasing trend. The land presents the largest temperature anomalies as well as the most prominent changes, followed by the land-ocean and the ocean. We concluded that the TSI has a fundamental role in the temperature behavior over the long-term. • We obtained temperature anomalies using a high and low IPCC-5 CO 2 emission scenarios and the Total Solar Irradiance (TSI). • For high CO 2 emission, the inclusion of the TSI prevents the temperature from having a runaway behavior. • For low CO 2 emission with no TSI, the temperature anomaly after 2075 is constant, presenting a decreasing trend with the TSI. • The TSI presents three future secular minima, but they only introduce a perturbation in the general decreasing trend. • We concluded that the TSI has a fundamental role in the temperature behavior over the long-term. [ABSTRACT FROM AUTHOR]

• Temporal variability of solar-atmospheric links reveals a ∼60-year periodicity. • The evolution of the stratospheric polar vortex is a possible reason for this variability. • Total solar irradiance variations may influence the polar vortex state. In this work we continue studying possible reasons for temporal variability observed in correlation links between characteristics of the lower atmosphere and solar activity phenomena at the multidecadal time scale. Temporal variations of correlation coefficients between troposphere pressure at extratropical latitudes and sunspot numbers are compared with the evolution of the large-scale circulation forms according to the Vangengeim-Girs classification, as well as the characteristics of the stratospheric polar vortex and global temperature anomalies. The results obtained show that temporal variability of solar activity/galactic cosmic ray (SA/GCR) effects on troposphere pressure (the development of extratropical baric systems) is characterized by a roughly 60-year periodicity and closely related to changes in the regime of large-scale circulation which accompany transitions between the different states of the polar vortex. It was suggested that the character of SA/GCR effects depends on the polar vortex strength influencing the troposphere-stratosphere coupling. It was shown that the evolution of the polar vortex may be associated with global temperature variations, with a possible reason for these variations being long-term changes of total solar irradiance. [ABSTRACT FROM AUTHOR]

A reevaluation of the solar constant is undertaken here to take into account the progress in space radiometry that has occurred since the early 2000s. Various sources of spaceborne total solar irradiance (TSI) observations are investigated here, including the long-term ACRIM and PMOD composites, as well as recent observations from the SORCE-TIM, TCTE-TIM, and PICARD-PREMOS instruments. A proxy model is constructed using daily data of sunspot number, radio flux at 10.7 cm, and MgII index, as predictors for TSI over the 42-year period 1976–2017. These daily estimates are used to fill in 9.7% of missing TSI observations during that period. By comparison with these proxy estimates, the PMOD composite appears generally more reliable than the ACRIM composite before 2003, and particularly before 1981. The 42-year time span is separated into nine periods, each defining the revised TSI daily values from one or more sources that are selected based on the trend of their resemblance with the proxy model. A final correction is added to emulate the highly accurate absolute calibration of PREMOS. Based on the resulting TSI reconstruction, a revised solar constant value of 1361.1 W/m 2 is obtained, with a standard uncertainty of 0.5 W/m 2 . The revised solar constant is ≈5 W/m 2 less than the previous values promulgated in ASTM and ISO standards. A revision of these standards is thus highly recommended. [ABSTRACT FROM AUTHOR]

A continuous record of direct total solar irradiance (TSI) observations began with a series of satellite experiments in 1978. This record requires comparisons of overlapping satellite observations with adequate relative precisions to provide useful long term TSI trend information. Herein we briefly review the active cavity radiometer irradiance monitor physikalisch-meteorologisches observatorium davos (ACRIM-PMOD) TSI composite controversy regarding how the total solar irradiance (TSI) has evolved since 1978 and about whether TSI significantly increased or slightly decreased from 1980 to 2000. The main question is whether TSI increased or decreased during the so-called ACRIM-gap period from 1989 to 1992. There is significant discrepancy between TSI proxy models and observations before and after the gap, which requires a careful revisit of the data analysis and modeling performed during the ACRIM-gap period. In this study, we use three recently proposed TSI proxy models that do not present any TSI increase during the ACRIM-gap, and show that they agree with the TSI data only from 1996 to 2016. However, these same models significantly diverge from the observations from 1981 and 1996. Thus, the scaling errors must be different between the two periods, which suggests errors in these models. By adjusting the TSI proxy models to agree with the data patterns before and after the ACRIM-gap, we found that these models miss a slowly varying TSI component. The adjusted models suggest that the quiet solar luminosity increased from the 1986 to the 1996 TSI minimum by about 0.45 W/m2 reaching a peak near 2000 and decreased by about 0.15 W/m2 from the 1996 to the 2008 TSI cycle minimum. This pattern is found to be compatible with the ACRIM TSI composite and confirms the ACRIM TSI increasing trend from 1980 to 2000, followed by a long-term decreasing trend since.

The Earth Radiation Budget at the top of the atmosphere quantifies how the Earth gains energy from the Sun and loses energy to space. It is of fundamental importance for climate and climate change. In this paper, the current state-of-the-art of the satellite measurements of the Earth Radiation Budget is reviewed. Combining all available measurements, the most likely value of the Total Solar Irradiance at a solar minimum is 1362 W/m², the most likely Earth albedo is 29.8%, and the most likely annual mean Outgoing Longwave Radiation is 238 W/m². We highlight the link between long-term changes of the Outgoing Longwave Radiation, the strengthening of El Nino in the period 1985-1997 and the strengthening of La Nina in the period 2000-2009. [ABSTRACT FROM AUTHOR]

How did the Sun affect the air pollution on the Earth? There are few papers about this question. This work investigates the relationship between the air pollution and solar activity by using the geophysical and environmental data during the period of 2000-2016. It is quite certain that the solar activity may impact on the air pollution, but the relationship is very weak and indirect. The Pearson correlation, Spearman rank correlation, Kendall's rank correlation, and conditional probability were adopted to analyze the air pollution index (API), air quality index (AQI), sunspot number (SSN), radio flux at wavelength of 10.7 cm (F10.7), and total solar irradiance (TSI). The analysis implies that the correlation coefficient between API and SSN is weak ( $-0.17< r<0.32$ ) with complex variation. The main results are: (1) For cities with higher air pollution, the probability of high API will be increased along with SSN, then reach to a maximum, and then decreased; (2) For cities with lower air pollution, the API has lower correlation with SSN; (3) The relationship between API and F10.7, or API and TSI are also similar as API and SSN. The solar activities take direct effect on TSI and the energetic particle flux, and indirect and long-term effect on lower atmosphere and weather near the Earth. All of these factors contribute to the air pollution on the Earth. [ABSTRACT FROM AUTHOR]

The effects of total solar irradiance (TSI) and volcanic activity on long-term global temperature variations during solar cycles 19–23 were studied. It was shown that a large proportion of climate variations can be explained by the mechanism of action of TSI and cosmic rays (CRs) on the state of the lower atmosphere and other meteorological parameters. The role of volcanic signals in the 11-year variations of the Earth's climate can be expressed as several years of global temperature drop. Conversely, it was shown that the effects of solar, geophysical, and human activity on climate change interact. It was concluded that more detailed investigations of these very complicated relationships are required, in order to be able to understand issues that affect ecosystems on a global scale. [ABSTRACT FROM AUTHOR]

During interplanetary flight, after large solar flares, astronauts are subject to the impact of relativistic solar protons. These particles produce an especially strong effect during extravehicular activity or landing on Mars (in the future). The relativistic protons reach the orbits of the Earth and Mars with a delay of several hours relative to solar X-rays and UV radiation. In this paper, we discuss a new opportunity to predict the most dangerous events caused by Solar Cosmic Rays with protons of maximum (relativistic) energy, known in the of solar-terrestrial physics as Ground Level Enhancements or Ground Level Events (GLEs) . This new capability is based on a close relationship between the dangerous events and decrease of Total Solar Irradiance (TSI) which precedes these events. This important relationship is revealed for the first time. [ABSTRACT FROM AUTHOR]

• A high resolution ostracod record was obtained from Dalongchi Lake in ACA. • An overall humid but with unstable climate were detected during the LIA. • Solar activity dominated the multidecadal-scale climate fluctuations during the LIA. • The Gleissberg solar cycle affected regional humidity changes by evaporative forcing. Climatic instability has major impacts on water resources and catastrophic effects on fragile ecosystems in arid Central Asia (ACA). Short-term (decadal to centennial) climate fluctuations over the last millennium can help predict whether future climate instability and the frequency of extreme climate events will increase. Research has revealed higher moisture variability during the Little Ice Age (LIA) than during the Medieval Warm Period (MWP). However, the age control quality and temporal resolution of the proxy records that are used make it difficult to characterize the specific unstable climate fluctuations on decadal to centennial scales. Here, we present a well‐dated high‐resolution ostracod record from a remote alpine lake (Dalongchi Lake) in the central Tianshan Mountains, northwestern China, ACA, which has an average ∼ 3–4-year resolution and provides a record of inferred lake level fluctuations over the past millennium. The abundance of deep-water adapted Fabaeformiscandona gyirongensis was generally higher in the LIA and lower in the MWP and Current Warm Period (CWP), which confirmed the associations of warm–dry and cold–wet conditions in ACA. Notably, our ostracod records captured several distinct and dramatic secondary lake level fluctuations during the LIA. The abundance of F. gyirongensis peaked in four intervals at 1380–1460, 1540–1580, 1640–1720 and 1800–1940 CE, indicating sharp lake level increases, while the abundance decreased sharply in the three intervals of 1460–1540, 1580–1640 and 1720–1800 CE, indicating significant lake level decreases. There was a strong, inverse relationship between the lake level and the total solar irradiance (TSI) on the multidecadal to centennial scale, and the spectral analysis and wavelet coherence results suggest the presence of Gleissberg cycles. We propose that the century Gleissberg solar cycle directly affected regional humidity changes through temperature and evaporation forcing. Our findings suggest that solar activity probably plays an important role in determining future hydroclimatic changes in ACA. [ABSTRACT FROM AUTHOR]

Aims: We characterize the solar rotational modulations of spectral solar irradiance (SSI) and compare them with the corresponding changes of total solar irradiance (TSI). Solar rotational modulations of TSI and SSI at wavelengths between 120 and 1600 nm are identified over one hundred Carrington rotational cycles during 2003–2013. Methods: The SORCE (Solar Radiation and Climate Experiment) and TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics)/SEE (Solar EUV Experiment) measured and SATIRE-S modeled solar irradiances are analyzed using the EEMD (Ensemble Empirical Mode Decomposition) method to determine the phase and amplitude of 27-day solar rotational variation in TSI and SSI. Results: The mode decomposition clearly identifies 27-day solar rotational variations in SSI between 120 and 1600 nm, and there is a robust wavelength dependence in the phase of the rotational mode relative to that of TSI. The rotational modes of visible (VIS) and near infrared (NIR) are in phase with the mode of TSI, but the phase of the rotational mode of ultraviolet (UV) exhibits differences from that of TSI. While it is questionable that the VIS to NIR portion of the solar spectrum has yet been observed with sufficient accuracy and precision to determine the 11-year solar cycle variations, the temporal variations over one hundred cycles of 27-day solar rotation, independent of the two solar cycles in which they are embedded, show distinct solar rotational modulations at each wavelength.

The switching of the total solar irradiance (TSI) backup radiometer (PREMOS-B) to a primary role for 2 weeks at the end of the PICARD mission provides a unique opportunity to test the fundamental hypothesis of radiometer experiments in space, which is that the sensitivity change of instruments due to the space environment is identical for the same instrument type as a function of solar-exposure time of the instruments. We verify this hypothesis for the PREMOS TSI radiometers within the PREMOS experiment on the PICARD mission. We confirm that the sensitivity change of the backup instrument, PREMOS-B, is similar to that of the identically-constructed primary radiometer, PREMOS-A. The extended exposure of the backup instrument at the end of the mission allows for the assessment, with an uncertainty estimate, of the sensitivity change of the primary radiometer from the beginning of the PICARD mission compared to the end, and of the degradation of the backup over the mission. We correct six sets of PREMOS-B observations connecting October 2011 with February 2014, using six ratios from simultaneous PREMOS-A and PREMOS-B exposures during the first days of PREMOS-A operation in 2010. These ratios are then used, without indirect estimates or assumptions, to evaluate the stability of SORCE/TIM and SOHO/VIRGO TSI measurements, which have both operated for more than a decade and now show different trends over the time span of the PICARD mission, namely from 2010 to 2014. We find that by February 2014 relative to October 2011 PREMOS-B supports the SORCE/TIM TSI time evolution, which in May 2014 relative to October 2011 is ~0.11 W m−2, or ~84 ppm, higher than SOHO/VIRGO. Such a divergence between SORCE/TIM and SOHO/VIRGO over this period is a significant fraction of the estimated decline of 0.2 W m−2 between the solar minima of 1996 and 2008, and questions the reliability of that estimated trend. Extrapolating the uncertainty indicated by the disagreement of SORCE/TIM and PREMOS with respect to SOHO/VIRGO, we can conclude that it is currently not possible to assess centennial timescale changes in solar irradiance based on any of the presently existing TSI composites. It is imperative to accurately estimate solar irradiance changes from observations in order to extrapolate centennial scale trends important for understanding both long-term solar irradiance changes and the Sun’s influence on the Earth’s climate.

Aims. The existing records of total solar irradiance (TSI) since 1978 differ not only in absolute values, but also show different trends. For the study of TSI variability these records need to be combined and three composites have been devised; however, the results depend on the choice of the records and the way they are combined. A new composite should be based on all existing records with an individual qualification. It is proposed to use a time-dependent uncertainty for weighting of the individual records. Methods. The determination of the time-dependent deviation of the TSI records is performed by comparison with the square root of the sunspot number (SSN). However, this correlation is only valid for timescales of the order of a year or more because TSI and SSN react quite differently to solar activity changes on shorter timescales. Hence the results concern only periods longer than the one-year-low-pass filter used in the analysis. Results. Besides the main objective to determine an investigator-independent uncertainty, the comparison of TSI with √SSN turns out to be a powerful tool for the study of the TSI long-term changes. The correlation of √SSN with TSI replicates very well the TSI minima, especially the very low value of the recent minimum. The results of the uncertainty determination confirm not only the need for adequate corrections for degradation, but also show that a rather detailed analysis is needed. The daily average of all TSI values available on that day, weighted with the correspondingly determined uncertainty, is used to construct a “new” composite, which, overall, compares well with the Physikalisch-Meteorologisches Observatorium Davos (PMOD) composite. Finally, the TSI − √SSN comparison proves to be an important diagnostic tool not only for estimating uncertainties of observations, but also for a better understanding of the long-term variability of TSI.