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Copyright of Al-Mustansiriyah Journal of Science is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Lightning is one of the natural disasters that cause significant financial losses and even fatalities. Therefore, it is necessary to understand the characteristics of lightning and related factors take appropriate preventive and mitigation measures. This work investigated the influence of aerosols and atmospheric thermodynamic factors on lightning in Java Island using 16 years of data (1998 - 2013) from the Tropical Rainfall Measuring Mission (TRMM) satellite. Aerosol data were obtained from the Modern Era Retrospective Analysis for Research and Applications version 2 (MERRA-2). Furthermore, convective available potential energy (CAPE) and potential temperature data were taken from the fifth-generation ECMWF atmospheric reanalysis (ERA-5) data. The intensity of lightning strikes in the western part of Java, such as Jakarta and Banten, is higher than in the eastern part, corresponding to the distribution pattern of aerosols, especially sulfate aerosols, sea salt aerosols, and black carbon aerosols. Sea salt aerosols have an inverse relationship with lightning, as these coarse-sized aerosols tend to inhibit convection. An increase in CAPE and potential temperature generally leads to higher lightning intensity. However, in cases where CAPE values are extremely high, such as in Jakarta, the intensity of lightning decreases. A similar pattern can be observed with potential temperature. An inverse relationship between lightning and potential temperature is observed in regions at higher elevations. The peak time for CAPE and potential temperature coincide with the peak intensity of lightning, which typically occurs during the rainy season, while the peak of AOD occurs earlier, during the pre-monsoon (September-October-November). The highest values of sea salt AOD are observed during the dry season (June-July-August) when lightning is minimal. These variations in peak times are particularly evident in the western regions of Java, where AOD values are high. The findings of this study can aid in lightning disaster mitigation efforts on Java Island. [ABSTRACT FROM AUTHOR]

Studying the heat flux in the boundary layer and understanding its relationship to the various atmospheric variables reflects positively on understanding the nature of turbulence in this layer and thus understanding the nature of the spread and movement of pollutants and the transmission and distribution of energy in this layer, also, the vertical heat flux is considered a significant influence on the movement of buoyancy and stability in the boundary layer and its effect on the horizontal wind movement, and therefore it is considered one of the important studies indirectly involved in the estimates of wind energy production, pollutant diffusion, and turbulence. This study involved the calculation of the Eddy Heat Flux and turbulent kinetic energy across Baghdad city. Our investigation revealed a correlation between the Eddy Heat Flux, temperature, and Turbulent Kinetic Energy (TKE). The observations have been made for wind speed with three components (u, v, w) and temperature by using a fast-response anemometer. As for the atmospheric pressure data, it was obtained from the automatic weather station located in the department of Atmospheric Sciences at Mustansiriyah University. The range of observations extended through the duration of thirty days for 24 hours from 1st July 2016 to 30th July 2016 every second. The maximum Eddy Heat Flux value was 0.092 J/(m2.s) at 10:00 on 23th July 2016, while the minimum Eddy Heat Flux value was -0.013 J/(m2.s) at 21:00 hour on 25th July 2016, the negative sign refer to a change in the direction of heat transfer,. It was also found that there is a positive relationship between the eddy heat flux and temperatures with a correlation coefficient of 0.93, as well as between the eddy heat flux and the turbulent kinetic energy with a correlation coefficient of 0.8.

The compositions and volumes of basalt generated by partial melting of the Earth's mantle provide fundamental constraints on the thermo-chemical conditions of the upper mantle. However, using melting products to interpret uniquely these conditions is challenging given the complexity of the melting and melt aggregation processes. Forward models simulating melting of lithologically heterogeneous mantle sources can account for this complexity, but require assumptions about key model input parameters, and the quality of the model fits to the observations are rarely, if at all, considered. Alternatively, inverse melting models can provide estimates of the quality of model fits to the observations, but as of yet, do not account for the presence of lithologic heterogeneity in the mantle source. To overcome these limitations, we present an inverse method coupling a Markov chain Monte Carlo (MCMC) sampling method with the REEBOX PRO forward mantle melting model. We use this tool to constrain mantle potential temperature, melt volumes, and the trace element and isotopic compositions of mantle source lithologies beneath the Reykjanes Peninsula of Iceland. We consider a range of plausible pyroxenite compositions (KG1, G2, and MIX1G) that span much of the range of natural pyroxenite compositions, and constrain the mantle potential temperature between 1455 and 1480 °C and pyroxenite abundance between 6.5 and 8.5%. These results are independent of the choice of pyroxenite composition and indicate that elevated potential temperatures and modest pyroxenite abundances are robust features of the Reykjanes Peninsula mantle source. The permitted ranges of pyroxenite trace element compositions vary as a function of pyroxenite fertility and mineralogy, but differ from the compositions of subduction-modified recycled oceanic crust typically used in previous models, indicating a more complex petrogenetic origin for the pyroxenite source than previously considered. As all of the pyroxenites employed here yield equally good fits to the geochemical and geophysical observations along the Reykjanes Peninsula, forward models should not be used to constrain the major element character of pyroxenite present in mantle source regions based solely on the trace element/isotopic compositions (and volumes) of basalts. Given the range of lithologies included in REEBOX PRO and the flexibility of MCMC inversion, this method may be applied to constrain thermal and compositional source characteristics in a wide variety of basalt source regions.

The compositions and volumes of basalt generated by partial melting of the Earth's mantle provide fundamental constraints on the thermo-chemical conditions of the upper mantle. However, using melting products to interpret uniquely these conditions is challenging given the complexity of the melting and melt aggregation processes. Forward models simulating melting of lithologically heterogeneous mantle sources can account for this complexity, but require assumptions about key model input parameters, and the quality of the model fits to the observations are rarely, if at all, considered. Alternatively, inverse melting models can provide estimates of the quality of model fits to the observations, but as of yet, do not account for the presence of lithologic heterogeneity in the mantle source. To overcome these limitations, we present an inverse method coupling a Markov chain Monte Carlo (MCMC) sampling method with the REEBOX PRO forward mantle melting model. We use this tool to constrain mantle potential temperature, melt volumes, and the trace element and isotopic compositions of mantle source lithologies beneath the Reykjanes Peninsula of Iceland. We consider a range of plausible pyroxenite compositions (KG1, G2, and MIX1G) that span much of the range of natural pyroxenite compositions, and constrain the mantle potential temperature between 1455 and 1480 °C and pyroxenite abundance between 6.5 and 8.5%. These results are independent of the choice of pyroxenite composition and indicate that elevated potential temperatures and modest pyroxenite abundances are robust features of the Reykjanes Peninsula mantle source. The permitted ranges of pyroxenite trace element compositions vary as a function of pyroxenite fertility and mineralogy, but differ from the compositions of subduction-modified recycled oceanic crust typically used in previous models, indicating a more complex petrogenetic origin for the pyroxenite source than previously considered. As all of the pyroxenites employed here yield equally good fits to the geochemical and geophysical observations along the Reykjanes Peninsula, forward models should not be used to constrain the major element character of pyroxenite present in mantle source regions based solely on the trace element/isotopic compositions (and volumes) of basalts. Given the range of lithologies included in REEBOX PRO and the flexibility of MCMC inversion, this method may be applied to constrain thermal and compositional source characteristics in a wide variety of basalt source regions.

The data of NCEP reanalysis （1°×1°）， national ground automatic stations， radiosonde and Sichuan encrypted automatic stations were used to diagnose the three definitions potential temperature and potential vorticity in an extreme rainstorm which occurred in the western Sichuan Basin during August 15 -18， 2020.The results indicate that： Rainfall occurs in the ‘high east and low west’ circulation in the 500 hPa， the low-level shear line and vortex are the favorable dynamic conditions.There is an obvious pseudo-equivalent potential temperature and generalized potential temperature （θ* ） gradient in the heavy rain area， but potential temperature is not.Potential vorticity （PV） anomaly area corresponds well to the precipitation area near 500 hPa and 800 hPa.In the mid-low troposphere， the overlapping area of the negative vertical component （MPV1） and horizontal component （MPV2） of moist potential vorticity， and negative MPV1 in lower level， positive in higher level are warning areas of the storm.Meanwhile， the rainfall center is close to the negative and positive junction area of MPV1， and the rainstorm was mainly affected by convective instability in the low troposphere.The generalized moist potential vorticity （GMPV） abnormal disturbance area in 800~600 hPa can be used as the rainstorm warning area， and its positively correlated with the change of low-level water vapor.The space-time distribution of three definitions potential vorticity and precipitation have a good correspondence in a single station， and the precipitation intensity is positively correlated with the disturbance intensity.The indicated height of PV， MPV and GMPV is 650~550 hPa， 600~500 hPa and 800 hPa.Three definitions potential temperature has obvious difference， which the θ* can best reflect the high-water vapor of rainstorm.

This work stems from the idea of improving the capability to measure the atmospheric boundary layer height (ABLH) in variable or unstable weather conditions or in the presence of turbulence and precipitation events. A new approach based on the use of rotational and roto-vibrational Raman lidar signals is considered and tested. The traditional gradient approach based on the elastic signals at wavelength 532 nm is also considered. Lidar data collected by the University of Basilicata Raman lidar (BASIL) within the Special Observation Period 1 (SOP 1) in Cardillargues (Ceveninnes–CV supersite) during the Hydrological Cycle in the Mediterranean Experiment (HyMeX) were used. Our attention was specifically focused on the data collected during the period 16–21 October 2012. ABLH estimates from the Raman lidar were compared against other innovative methods, such as the recently established Morphological Image Processing Approach (MIPA) and the temperature gradient technique applied to potential temperature obtained from radio-sounding data. For each considered methodology, a statistical analysis was carried out. In general, the results from the different methodologies are in good agreement. Some deviations have been observed in correspondence with quite unstable weather conditions. [ABSTRACT FROM AUTHOR]

Globally, a variety of numerical weather prediction (NWP) models are employed by national agencies. However, the derived outputs from these models are generally inadequate for precise cultivation management due to bias error. This study uses observational data acquired over several months to develop an equation for correcting surface air temperature (SAT) error in NWP model outputs. With the proposed method, model outputs are converted into potential temperature to cancel the influence of differences between computational elevation and real elevation. The potential temperature errors in the NWP model outputs are corrected using a linear regression equation in which a radiative cooling scale (RCS) serves as the independent variable. The RCS is computed using air temperature observed at a nearby meteorological observation station, together with upper‐level pressure data from the NWP model. Versions of the correction models are developed for specific situations: day, night, and upper‐level meteorology, classified into six groups. In an application of the proposed method, the root mean square error (RMSE) of the corrected SAT output from a global spectral model operated by the Japan Meteorological Agency (JMA) was 1.2–1.6 K; the RMSE of the corrected SAT output from a nonhydrostatic model operated by the JMA was 1.2–1.5 K. The proposed method corrected the NWP model SAT output errors to a level of accuracy similar to that of data corrected using the Kalman filtering technique without the requirement for constant observation at the target site. [ABSTRACT FROM AUTHOR]

This research is aimed to investigate the types of inversions and their intensity using atmospheric thermodynamic indices such as SI, LI, KI, and TT indices in Ahwaz station from 2010 to 2020. In this research, atmospheric upper-air sounding data from Ahwaz Synoptic Station for 00:00 GMT (local 3:30 am) during the last 11 years (2010 to 2020) and 11 km above sea level were obtained from the University of Wyoming. The results showed that the average number of events of temperature inversion in Ahwaz is 467 cases per year, of which about 28.8% is radiation temperature inversion, 9% to frontals, and the other 62.2% is temperature inversion of subsidence type. Due to air subsidence under subtropical high pressure, the share of subsidence inversions is higher than other types of inversions. But in terms of intensity, the most severe temperature inversion in Ahwaz was radiation type. The results of the intensity coefficient showed that whenever the thickness layer is less, the air temperature is higher, the incidence height is lower, the layer pressure is higher, inversion occurs near the earth's surface, and the severity of inversion is also increasing, which will have devastating consequences for human health and the environment. The relationship between inversion intensity and temperature, pressure, and height parameters showed that there was an inverse and significant relationship between inversion intensity values with thickness and height. The lower the height and thickness of the layer, the more intense the inversion becomes, but the relationship between the intensity coefficient and the temperature of the layer is direct and significant so that the higher the temperature of the layer, the more severe the inversion occurred will be and vice versa. Also, the relationship between inversion intensity and atmospheric gases showed that with the increase in the amounts of these gases, the inversion severity in the city of Ahwaz has also increased significantly. [ABSTRACT FROM AUTHOR]

In this study, we examine the influence of the mantle and large-scale tectonics on the global mid-ocean ridge (MOR) system. Using solely seismically-inferred upper mantle temperatures below the melting zone (260-600 km) and an interpretable machine learning model (Random Forest and Principal Component Analysis), we can predict a priori the location (ocean basin and ridge system) of global MOR with up to 90% accuracy. Two features provide > 50% of the discriminative power: the temperature difference between the mid-layer (340-500 km) and other depths, and the depth-averaged temperature of the upper mantle. We suggest long-term (100s Myr) tectonic and large-scale convective processes primarily driven by deep subduction left ample, distinct but hidden fingerprints in the mantle that allow us to separate regions at ∼1000 km scale. Our result implies that the large-scale geophysical and geochemical differences observed along the MOR system are reflective, not primarily of shallow processes associated with melting, but of the integrated long-term tectonic, subduction, and convective flow history that determines the present-day upper mantle temperature structure. • Mantle temperatures beneath global mid-ocean ridges exhibit inter- basin differences. • We use machine learning to predict the geographic location of ridge segments based on the sub-ridge upper mantle temperature. • The integrated history of convection and tectonics is recorded in the large-scale patterns observed at mid-ocean ridges. [ABSTRACT FROM AUTHOR]

Abstract Globally, a variety of numerical weather prediction (NWP) models are employed by national agencies. However, the derived outputs from these models are generally inadequate for precise cultivation management due to bias error. This study uses observational data acquired over several months to develop an equation for correcting surface air temperature (SAT) error in NWP model outputs. With the proposed method, model outputs are converted into potential temperature to cancel the influence of differences between computational elevation and real elevation. The potential temperature errors in the NWP model outputs are corrected using a linear regression equation in which a radiative cooling scale (RCS) serves as the independent variable. The RCS is computed using air temperature observed at a nearby meteorological observation station, together with upper‐level pressure data from the NWP model. Versions of the correction models are developed for specific situations: day, night, and upper‐level meteorology, classified into six groups. In an application of the proposed method, the root mean square error (RMSE) of the corrected SAT output from a global spectral model operated by the Japan Meteorological Agency (JMA) was 1.2–1.6 K; the RMSE of the corrected SAT output from a nonhydrostatic model operated by the JMA was 1.2–1.5 K. The proposed method corrected the NWP model SAT output errors to a level of accuracy similar to that of data corrected using the Kalman filtering technique without the requirement for constant observation at the target site.

Copyright of Plateau Meteorology is the property of Plateau Meteorology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In Japan, several local strong winds that are unique to a particular region are known by names such as "oroshi," "dashi," and "kaze," including Akagi‐oroshi and Kiyokawa‐dashi. In the area around Kobe City, northerly downslope winds from Mt. Rokko, or "Rokko‐oroshi," blow. However, there have not been many studies on Rokko‐oroshi, and its nature is not yet fully known. In particular, the nature of Rokko‐oroshi in the middle of Mt. Rokko (34.7321°N, 135.2539°E) and temperature changes induced by the blow of Rokko‐oroshi have not been studied so far. For example, during the blowing of Rokko‐oroshi, wind speeds up to 12 m/s can be recorded at the downwind while experiencing a rapid temperature decrease of between 5 and 8°C. In this study, winds and temperatures in the middle of Mt. Rokko were observed to investigate the characteristics and temperature reduction effect of Rokko‐oroshi. First, characteristics of wind speed and direction in the middle of Mt. Rokko were clarified to determine the intensity and duration in which Rokko‐oroshi blew. Second, hourly changes in temperature, wind speed, and wind direction were analyzed to relate variations in wind speed and direction with temperature reductions upwind and downwind of Mt. Rokko and within Kobe City. Lastly, radiosonde measurements upwind and downwind of Mt. Rokko were inspected to elucidate the physical mechanisms necessary for the generation of Rokko‐oroshi. [ABSTRACT FROM AUTHOR]

Abstract In Japan, several local strong winds that are unique to a particular region are known by names such as “oroshi,” “dashi,” and “kaze,” including Akagi‐oroshi and Kiyokawa‐dashi. In the area around Kobe City, northerly downslope winds from Mt. Rokko, or “Rokko‐oroshi,” blow. However, there have not been many studies on Rokko‐oroshi, and its nature is not yet fully known. In particular, the nature of Rokko‐oroshi in the middle of Mt. Rokko (34.7321°N, 135.2539°E) and temperature changes induced by the blow of Rokko‐oroshi have not been studied so far. For example, during the blowing of Rokko‐oroshi, wind speeds up to 12 m/s can be recorded at the downwind while experiencing a rapid temperature decrease of between 5 and 8°C. In this study, winds and temperatures in the middle of Mt. Rokko were observed to investigate the characteristics and temperature reduction effect of Rokko‐oroshi. First, characteristics of wind speed and direction in the middle of Mt. Rokko were clarified to determine the intensity and duration in which Rokko‐oroshi blew. Second, hourly changes in temperature, wind speed, and wind direction were analyzed to relate variations in wind speed and direction with temperature reductions upwind and downwind of Mt. Rokko and within Kobe City. Lastly, radiosonde measurements upwind and downwind of Mt. Rokko were inspected to elucidate the physical mechanisms necessary for the generation of Rokko‐oroshi.

Conservation of entropy or potential temperature and accurate representation of wave propagation without computational modes are both desirable properties for a numerical model of the atmosphere. However, they appear to require different model formulations, forcing model developers to choose between them. Here it is shown that, by a straightforward modification of the horizontal entropy fluxes, numerical entropy conservation can be achieved without sacrificing accurate wave propagation. The result is confirmed by a numerical linear normal mode analysis for a simple but suitably modified finite‐volume scheme, and by buoyant bubble and gravity‐wave test cases in a vertical slice model using a suitably modified conservative semi‐Lagrangian transport scheme. [ABSTRACT FROM AUTHOR]

This work stems from the idea of improving the capability to measure the atmospheric boundary layer height (ABLH) in variable or unstable weather conditions or in the presence of turbulence and precipitation events. A new approach based on the use of rotational and roto-vibrational Raman lidar signals is considered and tested. The traditional gradient approach based on the elastic signals at wavelength 532 nm is also considered. Lidar data collected by the University of Basilicata Raman lidar (BASIL) within the Special Observation Period 1 (SOP 1) in Cardillargues (Ceveninnes–CV supersite) during the Hydrological Cycle in the Mediterranean Experiment (HyMeX) were used. Our attention was specifically focused on the data collected during the period 16–21 October 2012. ABLH estimates from the Raman lidar were compared against other innovative methods, such as the recently established Morphological Image Processing Approach (MIPA) and the temperature gradient technique applied to potential temperature obtained from radio-sounding data. For each considered methodology, a statistical analysis was carried out. In general, the results from the different methodologies are in good agreement. Some deviations have been observed in correspondence with quite unstable weather conditions.

We present a new algorithm, ReversePetrogen (RevPet), to infer mantle melting conditions (pressure, temperature, source composition) using evolved basalts that have experienced multiphase fractional crystallization. RevPet measures and minimizes the compositional distance between experimentally predicted phase saturation boundaries and an erupted basalt and the more primitive liquids that return it to a primary melt. We use RevPet to investigate mantle melting conditions at mid‐ocean ridges (MORs) using a global data set of 13,589 basaltic glasses. We find that their average apparent mantle potential temperature (TP*) is 1322°C ± 56°C with melting pressures of 13.0 ± 5 kbars. Inferring the true initial (pre‐melted) TP from TP* requires knowing the style and degree of melting of the input basalts. If MORB glasses were entirely produced by near‐fractional melting of a homogenous source, they would record the cooling of the mantle during melting from an initial TP = ∼1380°C (ΔTP = 0°C) down to TP = ∼1270°C. If, instead, they were all fully pooled near‐fractional melts of the same source, they would record variations in ambient MOR TP from ∼1300°C to 1450°C (ΔTP = 150°C). However, because MOR basalts are thought to be both near‐fractional and variably pooled melts of variable sources, MOR TP must be intermediate between these two extremes. Our best estimate, consistent with MOR crustal thickness, is that ambient MOR TP is homogenous (∼1350°C–1400°C) except near hotspots where TP reaches ∼1600°C. Some primitive glasses found near slow‐spreading ridges and back‐arcs record very low temperatures (TP* < 1250°C) and pressures of melting (<10 kbar) and reflect mantle cooling during melting and melt equilibration in the mantle lithosphere. Key Points: Most mid‐ocean ridge basalt glasses record apparent mantle potential temperatures of 1322°C ± 56°C (melting at 1334°C ± 55°C and 13.0 ± 5 kbars)We estimate that the ambient unmelted mid‐ocean ridge potential temperature is ∼1350°C–1400°C with localized hot regions (∼1600°C) near hotspotsOutlier primitive basaltic glasses from slow‐spreading ridges and back‐arcs record shallow low‐temperature peridotite melting <10 kbars [ABSTRACT FROM AUTHOR]

The examination of model error is fundamental to improve weather forecasts at any time‐scale. Here, model errors for two forecast lead times (12, 24 hr) at the grid‐point level are analysed using (a) the total Eulerian changes in variables, such as potential temperature and potential vorticity (PV), both conserved under adiabatic, frictionless conditions, and (b) Lagrangian diabatic tracers. The latter refines the Eulerian analysis by decomposing the total Eulerian changes into materially conserved and diabatically generated components. For both analyses, the behaviour of a theoretical unbiased model, for which the only assumption is that forecast error is zero when averaged over a large number of cases, is used as a reference. Deviations from this theoretical behaviour are used to highlight conditions leading to large errors. The analyses are performed on a set of forecasts produced with the UK Met Office Unified Model for a 25‐day period during the NAWDEX (North Atlantic Waveguide and Downstream Impact Experiment) field campaign (16 September–22 October 2016). The Eulerian approach indicates that changes in potential temperature and PV are underestimated with respect to the theoretical behaviour of an unbiased model. The grid points with the largest changes in 12 hr forecasts have the largest underestimation in the 24 hr forecast, highlighting the importance of the underestimation for the most dynamically and thermodynamically active grid points. The Lagrangian‐tracer investigation reveals very large deviations from the theoretical behaviour of an unbiased model regardless of the level of Eulerian change, in particular for PV, and an unrealistic similarity in magnitude between parametrized diabatic changes of PV in the 24 hr and 12 hr forecasts. This is at odds with what would be otherwise required to obtain unbiased behaviour. Addressing the deviations from the behaviour of a theoretical unbiased model found in this work could be a step forward towards an operational unbiased model. [ABSTRACT FROM AUTHOR]

To investigate the mechanisms for the record‐breaking rainfall in the coastal metropolitan city of Guangzhou, China during 6–7 May 2017, budget analyses of advection and source/sink terms of the water vapor, potential temperature, and vertical momentum equations were conducted using the model output of a nested very large eddy simulation with the Weather Research and Forecasting model. Results show that the warm and moist air flows from the south and east onshore in the lower troposphere provided the main moisture source for the heavy rainfall. The structure of vertical velocity and hydrometeors (low‐echo centroid structure), in which the heavy rainfall was separated from the low‐level updraft, was favorable for the formation and maintenance of a heavy precipitation rate. The removal of the heat due to the advection (cooling tendency) in the upper troposphere increased the convective available potential energy of parcels rising from the lower troposphere, maintaining the development of updrafts. Although the total buoyancy forcing was the main contribution term for maintaining the updrafts, total dynamic acceleration played an important role in the vertical acceleration below the maximum vertical velocity core. In particular, the nonlinear dynamic perturbation pressure gradient force in the lower troposphere induced by the rotations aloft maintained the strong updrafts. Key Points: Budgets of moisture, momentum, and heat were computed to study the mechanism for the record‐breaking rainfall in Guangzhou, ChinaThe persistent onshore warm and moist mesoscale flow from the south and east in the lower troposphere provided the main fuelBuoyancy and dynamic acceleration and the shallow weak cool pools jointly supported the sustained and strong slantwise updrafts [ABSTRACT FROM AUTHOR]

We conduct a sensitivity study of the North Atlantic cyclone climate, with respect to the cumulus parameterization (CP) and planetary boundary layer (PBL) schemes, applied in the dynamical downscaling of HadGEM2‐ES simulations using Polar Weather Research and Forecasting. A set of seven sensitivity experiments is conducted for 1979–2004 using these CP and PBL schemes. CP schemes are Kain‐Fritsch (KF), Zhang‐McFarlane (ZM), and the modified Tiedtke (TZ). PBL schemes are the local Mellor‐Yamada‐Janjić (MYJ), Mellor‐Yamada‐Nakanishi‐Niino Level 2.5 (MYNN2) schemes, and nonlocal Yonsei University (YSU) scheme. In terms of cyclone intensities, our results show that the fine‐resolution Weather Research and Forecasting simulations capture higher intensities of summer cyclones than the HadGEM2‐ES results, in better agreement with the ERA‐Interim reanalysis, and exhibit a weak sensitivity to CP and PBL schemes. However, the frequency of summer cyclones is quite sensitive to CP and PBL schemes. Four KF experiments suggest comparable numbers of cyclone tracks as derived from ERA‐Interim reanalysis data, which is about 21% more than the ZM‐MYJ or TZ experiments and 11% more than HadGEM2‐ES results. Larger tropospheric potential vorticity and more cyclogenesis in the KF simulation than in TZ or ZM simulations are associated with different cyclone triggering functions and different vertical distributions of heating. We also find increased cyclone activities over the North Atlantic in the YSU or MYNN2 schemes compared to MYJ, but results also depend on the KF CP scheme. This can be attributed to stronger vertical mixing in YSU and MYNN schemes, resulting in smaller static stability and enhanced atmospheric moisture. Key Points: The frequency of North Atlantic cyclones exhibits large sensitivity to the cumulus (CP) and planetary boundary layer (PBL) schemesThe intensity of North Atlantic summer cyclones is insensitive to the CP and PBL schemesLapse rate of potential temperature associated with CP, static stability, and turbulent moisture in the PBL has impact on cyclone activities [ABSTRACT FROM AUTHOR]

The energy budgets of the ocean play a crucial role in the analysis of climate change. Potential temperature is traditionally used as a conservative quantity to express variations associated with "heat" in oceanography, such as the heat content and heat transport. However, potential temperature is usually not conserved during turbulent mixing, so the use of conservative temperature is more accurate. Based on climatological simulations under the modern and Last Glacial Maximum (LGM; ~21 ka; ka=thousand years ago), as well as a transient climate simulation of the past 22 000 years, we quantify the errors induced by the neglect of the non-conservation of potential temperature in paleo-climate research for the first time. The temperature error reaches 0.9°C near the coasts affected by river discharges but is much smaller in the open oceans, typically 0.03°C above the main thermocline and less than 0.01°C elsewhere. The error of the ocean heat content (OHC) is roughly 3×1022 J and is relatively steady over the past 22 000 years. However, the OHC increases to six times the original value during the last glacial termination from 20 ka to 7 ka. As a result, the relative OHC error decreases from 1.2% in the LGM climate to 0.14% in the modern climate. The error of the ocean meridional heat transport (OMHT) is generally smaller than 0.005 PW (1 PW=1015 W), with very small temporal variations (typically 0.000 4 PW), and induces a relative OMHT error of typically 0.3% over the past 22 000 years. Therefore, the neglect of the non-conservation of potential temperature induces a relative error of generally less than 1% in the analyses of basin-scale climate variations. [ABSTRACT FROM AUTHOR]

The Monin-Obukhov similarity theory-based wind speed and potential temperature profiles are inherently coupled to each other. We have developed hybrid approaches to disentangle them, and as a direct consequence, the estimation of Obukhov length (and associated turbulent fluxes) from either wind-speed or temperature measurements becomes an effortless task. Additionally, our approaches give rise to two easily measurable indices of atmospheric stability. We compare these approaches with the traditional gradient and profile methods that require both wind-speed and temperature profile data. Using Monte-Carlo-type numerical experiments we demonstrate that, if the input profiles are free of any random errors, the performance of the proposed hybrid approaches is almost equivalent to the profile method and better than the gradient method. However, the proposed hybrid approaches are less competitive in comparison to their traditional counterparts in the presence of random errors. [ABSTRACT FROM AUTHOR]

Analyses of dropsonde data collected in Hurricane Edouard (2014) just after its mature stage are presented. These data have unprecedentedly high spatial resolution, based on 87 dropsondes released by the unmanned NASA Global Hawk from an altitude of 18 km during the Hurricane and Severe Storm Sentinel (HS3) field campaign. Attempts are made to relate the analyses of the data to theories of tropical cyclone structure and behaviour. The tangential wind and thermal fields show the classical structure of a warm‐core vortex, in this case with a secondary eyewall feature. Additionally, the equivalent potential temperature field (θe) shows the expected structure with a mid‐tropospheric minimum at outer radii and contours of θe flaring upwards and outwards at inner radii. With some imagination, these contours are roughly congruent to the surfaces of absolute angular momentum. However, details of the analysed radial velocity field are quite sensitive to the way in which the sonde data are partitioned to produce an azimuthal average. This sensitivity is compounded by an apparent limitation of the assumed steadiness of the storm over the period of data collection. Radius–height cross sections of selected fields derived from the dropsonde data: (a) tangential velocity component, contour interval 5 m/s, shading indicated on the side bar in m/s, and absolute angular momentum, black lines, contour interval 5 × 105 m2/s; (b) temperature perturbation, contour interval 2 K (positive values), 1 K (negative values), shading indicated on the side bar in K; (c) radial velocity component, contour interval 3 m/s, shading indicated on the side bar in m/s; (d) equivalent potential temperature, contour interval 10 K, shading indicated on the side bar in K, and absolute angular momentum, black lines, contours as in (a); (e) relative humidity, contour interval 10%, shading indicated on the side bar in %; and (f) a zoomed‐in version of (d) at heights below 3 km. [ABSTRACT FROM AUTHOR]

It has been hypothesized that the energy balance closure problem of single-tower eddy-covariance measurements is linked to large-scale turbulent transport. In order to shed light on this problem, we investigate the functional dependence of the normalized residual for the potential temperature and humidity conservation equations, i.e. the imbalance ratio for the fluxes of latent and sensible heat. We set up a suite of simulations consisting of cases with different stability and surface Bowen ratio. We employ a nesting approach in the lower part of the atmospheric boundary-layer to achieve higher spatial resolution near the surface. Our simulations reproduce earlier simulation results for the mixed layer and also mimic the saw-blade pattern of real flux measurements. Focusing on homogeneous terrain, we derive a parameterization for the spatially averaged flux imbalance ratios of latent and sensible heat in the surface layer. We also investigate how the remaining imbalance for a given point measurement is related to the local turbulence, by deriving a statistical model based on turbulence characteristics that are related to large-scale turbulence. The average imbalance ratio scales well with friction velocity, especially for sensible heat. For the latent heat flux, our results show that the Bowen ratio also influences the underestimation. Furthermore, in the surface layer the residual has a linear dependence on the absolute height divided by the boundary-layer height. Our parameterization allows us to deduce an expression for the residual in the energy budget for a particular measurement half hour, based on the measurement height and stability. [ABSTRACT FROM AUTHOR]