scholarly journals Climatology of Cloud Vertical Structures from Long-Term High-Resolution Radiosonde Measurements in Beijing

Atmosphere ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 401
Author(s):  
Qing Zhou ◽  
Yong Zhang ◽  
Shuze Jia ◽  
Junli Jin ◽  
Shanshan Lv ◽  
...  
Keyword(s):  
High Resolution ◽  
Atmospheric Circulation ◽  
Frequency Distribution ◽  
Hydrological Cycle ◽  
Global Radiation ◽  
Circulation Model ◽  
Middle Level ◽  
Radiation Budget ◽  
Cloud Base

Clouds are significant in the global radiation budget, atmospheric circulation, and hydrological cycle. However, knowledge regarding the observed climatology of the cloud vertical structure (CVS) over Beijing is still poor. Based on high-resolution radiosonde observations at Beijing Nanjiao Weather Observatory (BNWO) during the period 2010–2017, the method for identifying CVS depending on height-resolved relative humidity thresholds is improved, and CVS estimation by radiosonde is compared with observations by millimeter-wave cloud radar and ceilometer at the same site. Good consistency is shown between the three instruments. Then, the CVS climatology, including the frequency distribution and seasonal variation, is investigated. Overall, the occurrence frequency (OF) of cloudy cases in Beijing is slightly higher than that of clear-sky cases, and the cloud OF is highest in summer and lowest in winter. Single-layer clouds and middle-level clouds are dominant in Beijing. In addition, the average cloud top height (CTH), cloud base height (CBH), and cloud thickness in Beijing are 6.2 km, 4.0 km, and 2.2 km, respectively, and show the trend of reaching peaks in spring and minimums in winter. In terms of frequency distribution, the CTH basically resides below an altitude of 16 km, and approximately 43% of the CBHs are located at altitudes of 0.5–1.5 km. The cloud OF has only one peak located at altitudes of 4–8 km in spring, whereas it shows a trimodal distribution in other seasons. The height at which the cloud OF reaches its peak is highest in summer and lowest in winter. To the best of our knowledge, the cloud properties analyzed here are the first to elucidate the distribution and temporal variation of the CVS in Beijing from a long-term sounding perspective, and these results will provide a scientific observation basis for improving the atmospheric circulation model, as well as comparisons and verifications for measurements by ground-based remote sensing equipment.

scholarly journals Features of the Cloud Base Height and Determining the Threshold of Relative Humidity over Southeast China

2019 ◽  
Vol 11 (24) ◽  
pp. 2900 ◽  
Author(s):  
Yuzhi Liu ◽  
Yuhan Tang ◽  
Shan Hua ◽  
Run Luo ◽  
Qingzhe Zhu
Keyword(s):  
Relative Humidity ◽  
Hydrological Cycle ◽  
Critical Role ◽  
Global Radiation ◽  
Radiation Budget ◽  
Cloud Base ◽  
Accurate Information ◽  
Southeast China ◽  
Environmental Relative Humidity ◽  
Cloud Base Height

Clouds play a critical role in adjusting the global radiation budget and hydrological cycle; however, obtaining accurate information on the cloud base height (CBH) is still challenging. In this study, based on Lidar and aircraft soundings, we investigated the features of the CBH and determined the thresholds of the environmental relative humidity (RH) corresponding to the observed CBHs over Southeast China from October 2017 to September 2018. During the observational period, the CBHs detected by Lidar/aircraft were commonly higher in cold months and lower in warm months; in the latter, 75.91% of the CBHs were below 2000 m. Overall, the RHs at the cloud base were mainly distributed between 70 and 90% for the clouds lower than 1000 m, in which the most concentrated RH was approximately 80%. In addition, for the clouds with a cloud base higher than 1000 m, the RH thresholds decreased dramatically with increasing CBH, where the RH thresholds at cloud bases higher than 2000 m could be lower than 60%. On average, the RH thresholds for determining the CBHs were the highest (72.39%) and lowest (63.56%) in the summer and winter, respectively, over Southeast China. Therefore, to determine the CBH, a specific threshold of RH is needed. Although the time period covered by the collected CBH data from Lidar/aircraft is short, the above analyses can provide some verification and evidence for using the RH threshold to determine the CBH.

scholarly journals A global long term (1981–2019) daily land surface radiation budget product from AVHRR satellite data using a residual convolutional neural network

2021 ◽  
Author(s):  
Jianglei Xu ◽  
Shunlin Liang ◽  
Bo Jiang
Keyword(s):  
Neural Network ◽  
High Resolution ◽  
Convolutional Neural Network ◽  
Satellite Data ◽  
Land Surface ◽  
Radiant Energy ◽  
Surface Radiation ◽  
Radiation Budget ◽  
Surface Radiation Budget

Abstract. The surface radiation budget, also known as all-wave net radiation (Rn), is a key parameter for various land surface processes including hydrological, ecological, agricultural, and biogeochemical processes. Satellite data can be effectively used to estimate Rn, but existing satellite products have coarse spatial resolutions and limited temporal coverage. In this study, a point-surface matching estimation (PSME) method is proposed to estimate surface Rn using a residual convolutional neural network (RCNN) integrating spatially adjacent information to improve the accuracy of retrievals. A global high-resolution (0.05°) long-term (1981–2019) Rn product was subsequently generated from Advanced Very High-Resolution Radiometer (AVHRR) data. Specifically, the RCNN was employed to establish a nonlinear relationship between globally distributed ground measurements from 537 sites and AVHRR top of atmosphere (TOA) observations. Extended triplet collocation (ETC) technology was applied to address the spatial scale mismatch issue resulting from the low spatial support of ground measurements within the AVHRR footprint by selecting reliable sites for model training. The overall independent validation results show that the generated AVHRR Rn product is highly accurate, with R2, root-mean-square error (RMSE), and bias of 0.84, 26.66 Wm−2 (31.66 %), and 1.59 Wm−2 (1.89 %), respectively. Inter-comparisons with three other Rn products, i.e., the 5 km Global Land Surface Satellite (GLASS), the 1° Clouds and the Earth's Radiant Energy System (CERES), and the 0.5° × 0.625° Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA2), illustrate that our AVHRR Rn retrievals have the best accuracy under all of the considered surface and atmospheric conditions, especially thick cloud or hazy conditions. The spatiotemporal analyses of these four Rn datasets indicate that the AVHRR Rn product reasonably replicates the spatial pattern and temporal evolution trends of Rn observations. This dataset is freely available at https://doi.org/10.5281/zenodo.5509854 for 1981–2019 (Xu et al., 2021).

scholarly journals Comprehensive evaluations of diurnal NO<sub>2</sub> measurements during DISCOVER-AQ 2011: Effects of resolution dependent representation of NO<sub>x</sub> emissions

2021 ◽  
Author(s):  
Jianfeng Li ◽  
Yuhang Wang ◽  
Ruixiong Zhang ◽  
Charles Smeltzer ◽  
Andrew Weinheimer ◽  
...  
Keyword(s):  
High Resolution ◽  
Transport Model ◽  
Global Radiation ◽  
Vertical Mixing ◽  
Spatial Variations ◽  
Radiation Budget ◽  
Ozone Monitoring Instrument ◽  
Vertical Column ◽  
Model Simulations ◽  
Ozone Monitoring

Abstract. Nitrogen oxides (NOx = NO + NO2) play a crucial role in the formation of ozone and secondary inorganic and organic aerosols, thus affecting human health, global radiation budget, and climate. The diurnal and spatial variations of NO2 are functions of emissions, advection, deposition, vertical mixing, and chemistry. Their observations, therefore, provide useful constraints in our understanding of these factors. We employ a Regional chEmical and trAnsport model (REAM) to analyze the observed temporal (diurnal cycles) and spatial distributions of NO2 concentrations and tropospheric vertical column densities (TVCDs) using aircraft in situ measurements, surface EPA Air Quality System (AQS) observations, as well as the measurements of TVCDs by satellite instruments (OMI: the Ozone Monitoring Instrument; and GOME-2A: Global Ozone Monitoring Experiment – 2A), ground-based Pandora, and the Airborne Compact Atmospheric Mapper (ACAM) instrument, in July 2011 during the DISCOVER-AQ campaign over the Baltimore-Washington region. The model simulations at 36- and 4-km resolutions are in reasonably good agreement with the temporospatial NO2 observations in the daytime. However, nighttime mixing in the model needs to be enhanced to reproduce the observed NO2 diurnal cycle in the model. Another discrepancy is that Pandora measured NO2 TVCDs show much less variation in the late afternoon than simulated in the model. Relative to the 36-km model simulations, the 4-km model results show larger biases compared to the observations due largely to the larger spatial variations of NO2 in the model when the spatial resolution is increased from 36 to 4 km, although the biases are often comparable to the ranges of the observations. The high-resolution aircraft ACAM observations show a more dispersed distribution of NO2 vertical column densities (VCDs) and lower VCDs in urban regions than 4-km model simulations, reflecting likely the spatial distribution bias of NOx emissions in the National Emissions Inventory (NEI) 2011 at high resolution.

A study of Cloud Vertical Structure and its association with precipitation over Delhi.

2021 ◽  
Author(s):  
Saloni Sharma ◽  
Amit Kumar Mishra
Keyword(s):  
Vertical Structure ◽  
Prediction Models ◽  
Hydrological Cycle ◽  
Weather Prediction ◽  
Single Layer ◽  
Middle Level ◽  
Cloud Base ◽  
Frequency Of Occurrence ◽  
Monthly Average ◽  
Vertical Location

&lt;p&gt;Water in the atmosphere (in vapour, liquid or ice form) act as a fuel for various atmospheric processes through addition/removal of latent heat. Formation of clouds involves all these processes and thus it greatly affects atmospheric dynamics and thermodynamics. It is important to know the vertical location of clouds in atmosphere in order to understand it&amp;#8217;s effect on other important atmospheric variables. The interaction of cloud vertical distribution with other meteorological variables is very significant in determining the hydrological cycle of any region. Therefore, in this study we have found out the cloud vertical structure over Delhi and associated it with the precipitation. The cloud top height, base height and cloud thickness along with their vertical location in the atmosphere is known as cloud vertical structure (CVS). The association of CVS with precipitation involving the amount of precipitation contributed by different layers of cloud could be very helpful in weather prediction models. We have used the balloon based measurements to calculate the CVS and for precipitation we have used CHIRPS (Climate Hazards Group InfraRed Precipitation with Station data) data. We have done multiple regressions to determine association between Cloud top height, cloud base height and cloud depth with precipitation. We have also related the monthly average of precipitation with monthly frequency of occurrence of single-layer, double-layer and triple-layer clouds. The frequency of occurrence of clouds classified based on their altitude and depth ( i.e., low-level clouds, middle-level clouds, high-level clouds and deep convective clouds) are also correlated with the monthly average precipitation.&amp;#160;&lt;/p&gt;

scholarly journals Comparison of a global-climate model simulation to a cloud-system resolving model simulation for long-term thin stratocumulus clouds

2009 ◽  
Vol 9 (17) ◽  
pp. 6497-6520 ◽  
Author(s):  
S. S. Lee ◽  
J. E. Penner ◽  
M. Wang
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Model Simulation ◽  
Global Climate Model ◽  
Circulation Model ◽  
Radiation Budget ◽  
Cloud System ◽  
Cloud Base ◽  
Cumulus Clouds ◽  
Stratocumulus Clouds

Abstract. A case of thin, warm marine-boundary-layer (MBL) clouds is simulated by a cloud-system resolving model (CSRM) and is compared to the same case of clouds simulated by a general circulation model (GCM). In this study, the simulation by the CSRM adopts higher resolutions which are generally used in large-eddy simulations (LES) and more advanced microphysics as compared to those by the GCM, enabling the CSRM-simulation to act as a benchmark to assess the simulation by the GCM. Explicitly simulated interactions among the surface latent heat (LH) fluxes, buoyancy fluxes, and cloud-top entrainment lead to the deepening-warming decoupling and thereby the transition from stratiform clouds to cumulus clouds in the CSRM. However, in the simulation by the GCM, these interactions are not resolved and thus the transition to cumulus clouds is not simulated. This leads to substantial differences in liquid water content (LWC) and radiation between simulations by the CSRM and the GCM. When stratocumulus clouds are dominant prior to the transition to cumulus clouds, interactions between supersaturation and cloud droplet number concentration (CDNC) (controlling condensation) and those between rain evaporation and cloud-base instability (controlling cloud dynamics and thereby condensation) determine LWC and thus the radiation budget in the simulation by the CSRM. These interactions result in smaller condensation and thus smaller LWC and reflected solar radiation by clouds in the simulation by the CSRM than in the simulation by the GCM where these interactions are not resolved. The resolved interactions (associated with condensation and the transition to cumulus clouds) lead to better agreement between the CSRM-simulation and observation than that between the GCM-simulation and observation.

scholarly journals Scale-Invariant Formulation of Momentum Diffusion for High-Resolution Atmospheric Circulation Models

2018 ◽  
Vol 146 (4) ◽  
pp. 1045-1062 ◽  
Author(s):  
Urs Schaefer-Rolffs ◽  
Erich Becker
Keyword(s):  
High Resolution ◽  
Kinetic Energy ◽  
Atmospheric Circulation ◽  
Scale Invariance ◽  
General Circulation ◽  
Scaling Laws ◽  
Vertical Mixing ◽  
Circulation Model ◽  
Mixing Length ◽  
Scale Invariant

A new version of the dynamic Smagorinsky model is presented that applies for nonisotropic momentum diffusion in high-resolution atmospheric circulation models. While the horizontal mixing length is computed in accordance with scale invariance in the mesoscale regime of the horizontal energy cascade, the associated dynamic vertical mixing length (DVML) is based on a recently developed scale invariance criterion and represents an application of the scaling laws of stratified macroturbulence. The DVML is validated in high-resolution simulations with the Kühlungsborn mechanistic general circulation model, using triangular spectral truncation at wavenumber 330 and a vertical level spacing of about 200 m in the upper troposphere. For a proper choice of the test filter, the model simulates a realistic horizontal kinetic energy spectrum in the troposphere along with a realistic intensity of the Lorenz energy cycle. This result is obtained without any hyperdiffusion, and it depends only little on whether the vertical mixing length is prescribed or set to the DVML. The globally averaged Smagorinsky parameter is about c S ≅ 0.53. The latitude–height cross sections show that c S maximizes in regions of strong mesoscale kinetic energy.

scholarly journals Variability of global radiation under the influence of cloudiness, cloud types and atmospheric circulation in Southern Poland

2021 ◽  
Author(s):  
Dariusz Zajączkowski ◽  
Ewa Łupikasza
Keyword(s):  
Solar Radiation ◽  
Atmospheric Circulation ◽  
Extreme Values ◽  
Global Radiation ◽  
Meteorological Station ◽  
Annual Data ◽  
Southern Poland ◽  
Circulation Types ◽  
The Earth

&lt;p&gt;Solar radiation reaching the Earth&amp;#8217;s surface is a crucial energy source in the climate system and the primary factor regulating the planet energy balance. The amount of solar radiation reaching the Earth surface is conditioned by the atmosphere composition and its transparency that is determined by the content of aerosols, moisture and clouds. The G&amp;#243;rno&amp;#347;l&amp;#261;sko-Zag&amp;#322;&amp;#281;biowska Metropolis (GZM) located in southern Poland, is the most urbanized part of the country and one of the most polluted parts of Europe, which has an impact on the atmosphere transparency and amount of global radiation at the Earth's surface. This study aims to determine the daily and annual variability in global radiation and its relationship with cloudiness, selected cloud types and atmospheric circulation.&lt;/p&gt;&lt;p&gt;This study is based on unique 10-minute global radiation data measured in the centre of GZM&amp;#160; at the meteorological station of the faculty of Earth Sciences. The data covers the periods between 2002 and 2019. Average radiation intensity was converted into hourly and daily radiation sums expressed in MJ/m&lt;sup&gt;2&lt;/sup&gt;. Data on cloudiness were taken from the synoptic station Katowice Muchowiec located 9.6 km far from the meteorological station in GZM. The degree of cloud cover is expressed in a percentage of the sky covered with clouds. To analyse relationships between atmospheric circulation and global radiation, the calendar of circulation types and air masses for southern Poland was used.&lt;/p&gt;&lt;p&gt;Daily course calculated based on annual data showed that global radiation reached its highest values of 1.5 MJ/m&lt;sup&gt;2&lt;/sup&gt; at 10 UTC. The highest hourly sums of global radiation varied seasonally from about 0.5 MJ/m&lt;sup&gt;2&lt;/sup&gt; in winter to 2.0 MJ/m&lt;sup&gt;2&lt;/sup&gt; in summer. The widest range of variability in particular hours was found in spring (the quartiles: 1.2 - 2.0 MJ/m&lt;sup&gt;2&lt;/sup&gt;) and autumn (quartiles: 0.7 to 1.4 MJ/m&lt;sup&gt;2&lt;/sup&gt;). It occurred that most cloudiness classes enhanced the global radiation compared to cloudless conditions. The highest radiation sums were recorded during the days with a cloudiness &gt;0 and &amp;#8804;20%. During such days, global radiation was higher by 3.2 MJ/m&lt;sup&gt;2&lt;/sup&gt; than during cloudless days and 7.0 MJ/m&lt;sup&gt;2&lt;/sup&gt; than the long-term average 2002-2019. Daily global radiation was lower than the long-term average by about 3.0 MJ/m&lt;sup&gt;2&lt;/sup&gt; only during days with cloudiness &gt; 80%. Cirrus, cirrostratus, cirrocumulus and cumulus enhanced global radiation by about 40% compared to the long-term average. Altostratus, nimbostratus and stratus reduced the global radiation by about 75% compared to the long-term average. Global radiation also varied depending on circulation types. Extreme values of global radiation were registered under non-advective anticyclonic conditions and during southern advection (maximum 15.0 MJ/m&lt;sup&gt;2&lt;/sup&gt;) and during cyclonic types with air advection from the north (minimum 6.8 MJ/m&lt;sup&gt;2&lt;/sup&gt;)&lt;/p&gt;

scholarly journals Comparison of a global-climate model simulation to a cloud-system resolving model simulation for long-term thin stratocumulus clouds

2009 ◽  
Vol 9 (3) ◽  
pp. 12283-12344 ◽  
Author(s):  
S. S. Lee ◽  
J. E. Penner ◽  
M. Wang
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Model Simulation ◽  
Global Climate Model ◽  
Circulation Model ◽  
Radiation Budget ◽  
Cloud System ◽  
Cloud Base ◽  
Cumulus Clouds ◽  
Stratocumulus Clouds

Abstract. A case of thin, warm marine-boundary-layer (MBL) clouds is simulated by a cloud-system resolving model (CSRM) and is compared to the same case of clouds simulated by a general circulation model (GCM). In this study, the simulation by the CSRM adopts higher resolutions and more advanced microphysics as compared to those by the GCM, enabling the CSRM-simulation to act as a benchmark to assess the simulation by the GCM. Explicitly simulated interactions among the surface latent heat (LH) fluxes, buoyancy fluxes, and cloud-top entrainment lead to the deepening-warming decoupling and thereby the transition from stratiform clouds to cumulus clouds in the CSRM. However, in the simulation by the GCM, these interactions are not resolved and thus the transition to cumulus clouds is not simulated. This leads to substantial differences in cloud mass and radiation between simulations by the CSRM and the GCM. When stratocumulus clouds are dominant prior to the transition to cumulus clouds, interactions between supersaturation and cloud droplet number concentration (CDNC) (controlling condensation) and those between rain evaporation and cloud-base instability (controlling cloud dynamics and thereby condensation) determine cloud mass and thus the radiation budget in the simulation by the CSRM. These interactions result in smaller condensation and thus smaller cloud mass and reflected solar radiation by clouds in the simulation by the CSRM than in the simulation by the GCM where these interactions are not resolved. The resolved interactions (associated with condensation and the transition to cumulus clouds) lead to better agreement between the CSRM-simulation and observation than that between the GCM-simulation and observation.

scholarly journals Sensitivity of modelled sulfate aerosol and its radiative effect on climate to ocean DMS concentration and air–sea flux

2016 ◽  
Vol 16 (17) ◽  
pp. 10847-10864 ◽  
Author(s):  
Jan-Erik Tesdal ◽  
James R. Christian ◽  
Adam H. Monahan ◽  
Knut von Salzen
Keyword(s):  
General Circulation ◽  
Global Radiation ◽  
Circulation Model ◽  
Climate Impact ◽  
Radiation Budget ◽  
Spatial And Temporal Variability ◽  
Minor Effect ◽  
Radiative Effect ◽  
Space And Time ◽  
Global Mean

Abstract. Dimethylsulfide (DMS) is a well-known marine trace gas that is emitted from the ocean and subsequently oxidizes to sulfate in the atmosphere. Sulfate aerosols in the atmosphere have direct and indirect effects on the amount of solar radiation reaching the Earth's surface. Thus, as a potential source of sulfate, ocean efflux of DMS needs to be accounted for in climate studies. Seawater concentration of DMS is highly variable in space and time, which in turn leads to high spatial and temporal variability in ocean DMS emissions. Because of sparse sampling (in both space and time), large uncertainties remain regarding ocean DMS concentration. In this study, we use an atmospheric general circulation model with explicit aerosol chemistry (CanAM4.1) and several climatologies of surface ocean DMS concentration to assess uncertainties about the climate impact of ocean DMS efflux. Despite substantial variation in the spatial pattern and seasonal evolution of simulated DMS fluxes, the global-mean radiative effect of sulfate is approximately linearly proportional to the global-mean surface flux of DMS; the spatial and temporal distribution of ocean DMS efflux has only a minor effect on the global radiation budget. The effect of the spatial structure, however, generates statistically significant changes in the global-mean concentrations of some aerosol species. The effect of seasonality on the net radiative effect is larger than that of spatial distribution and is significant at global scale.

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