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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]

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.

• 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]

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. [ABSTRACT FROM AUTHOR]

Many Total Solar Irradiance (TSI) and Solar Constant (SC) values are given and used in the literature, sometimes leading to confusion. The TSI value is relevant and has great importance in engineering and scientific research in energy. In this study, a review has been done to study the TSI and SC concepts. A reevaluation of the TSI and SC is undertaken to consider state of the art. The effect of three different TSI values concerning different locations is studied for estimating global radiation with the Ångström-Prescott (A-P) formulation over Spain. New seasonal A-P coefficient sets are developed for Spain. The good performance for all the 29 stations and seasons and the slight differences observed for the different TSI values employed ensure global solar radiation (GSR) accuracy with the A-P model. The results highlight the local and seasonal A-P coefficient calibration relevance instead of using a single general pair of calibration coefficients. Based on the TSI study, we recommended calculations of solar radiation models to adopt the TSI value equal to 1361 W m−2. The revised TSI is lower than the previous values proposed. Therefore, it is highly recommended to review the value and concept of TSI. • A lower Total Solar Irradiance than the previous one is proposed. • High accuracy and precision are needed in environmental research and practice. • New seasonal A-P coefficient are provided over 29 meteorological stations. • A-P coefficient calibration should be considered instead of using a single pair. [ABSTRACT FROM AUTHOR]