| Precipitation and latent heat are important components of the Earth's energy and water cycle,they play an important role in maintaining the energy balance of the Earth System.Exploring the three-dimensional structure of precipitation and latent heat is the key to understand the cloud microphysical processes.Aerosols can act as condensation nuclei and promote the formation of precipitation,which in turn affects precipitation and latent heat.In recent years,the influence of aerosols on precipitation and latent heat has increasingly become a hot issue in atmospheric sciences.Due to the serious pollution in the Beijing-Tianj in-Hebei region,the corresponding aerosol emissions will affect precipitation and latent heat.To solve this problem,this paper uses MERRA-2 AOD data,GPM Level-2A(Ka/Ku and DPR),retrieval latent heat data and ERA5 reanalysis data to analyze the characteristics of precipitation profile and latent heat profile upon the influence of the aerosol optical thickness in the Beijing-Tianj in-Hebei region,the results are as follows:1.Check the MERRA-2 AOD data:This article uses MODIS AOD data to test the accuracy of MERRA-2 AOD data.According to cases and statistical results,it is found that the bias of the two AOD products is less than 0.1,and the correlation coefficient is above 0.7,it shows a good correlation,and the PDF distribution is also relatively similar.It can be seen that the MERRA-2 AOD data is a good substitute for MODIS AOD data.2.Study the profile under different precipitation characteristics:(1)Statistics of all precipitation samples:for the latent heat profile,the shape of the total latent heat profile is closer to the stratiform profile,with a height of 5km as the boundary,the latent heat is larger on the clean day above 5km,and the lower part is larger on the polluted day.The latent heat profile of convective precipitation shows a bimodal shape on the clean day,and the latent heat value is also small.The shape of the total precipitation profile is consistent with the convective precipitation profile and the stratiform precipitation profile.The precipitation rate is larger on the clean day above 4km,and larger on the polluted day below 4km.(2)Classified by the surface precipitation rate:for the latent heat profile,when the surface precipitation rate is small,the convective precipitation mostly presents a bimodal curve characteristic on the clean day,which the upper and lower peaks are located around 6km and 3 km respectively,and with the increase of surface precipitation rate,the phenomenon of double peaks gradually disappeared.On the polluted day,it shows a single-peak curve,which the peak is about 4km,the latent heat value is larger on the polluted day.Under the condition of different surface precipitation rates,the latent heat value is larger on the clean day in stratiform precipitation,and the height of the maximum latent heat is also higher.For the precipitation profile,the deep convective precipitation profile has a larger precipitation rate on the clean day above 4km and on the polluted day below 4km under the condition of different surface precipitation rates.However,the precipitation rate of the whole layer is large on the clean day in stratiform precipitation profile.(3)Classified by the height of the rain top:for the latent heat profile,when the rain top height is high in the convective precipitation,the upper peak is located around 2-3km below the height of the rain top,and the lower peak is located around 1-2km below the frozen layer,the latent heat profile shows a bimodal curve characteristic on the clean day,and the latent heat value is larger on the polluted day.The profile of stratiform precipitation is not much different between the polluted day and clean day above 5km,but the latent heat value is greater on the polluted day below 5km.For the precipitation profile,when the rain top height is above 4km,regardless of convective precipitation or stratiform precipitation,the upper part of the precipitation profile has the higher precipitation rate on the clean day,and the lower part has the higher precipitation rate on the polluted day.When the rain top height is less than 4km,the precipitation rate of the whole layer is lager on the clean day.3.Study the profile under different thermodynamic conditions:For the latent heat profile,when the 500hPa relative humidity and vertical velocity are low,the latent heat profile presents a bimodal curve in convective precipitation,the upper and lower peaks are located at about 6km and 3km respectively.When the 500hPa relative humidity and vertical velocity are high,the latent heat profile is a single-peak curve,and the latent heat value is lager on the polluted day.The latent heat profile of stratiform precipitation shows the opposite characteristics,the latent heat value is larger on the clean day,and the height of the maximum value of latent heat is also higher on the clean day.For the precipitation profile,when the 500hPa relative humidity and vertical velocity are low,the precipitation profile has the higher precipitation rate above 5km on a clean day regardless of the stratiform or the convective precipitation,and the lower part has the higher precipitation rate on the polluted day.When the 500hPa relative humidity and vertical velocity are high,the whole layer convective precipitation profile has a higher precipitation rate on the polluted day,but the stratiform precipitation profile does not change. |
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