The Study On Observation And Prarmeterization Of Cloud-Precipitation Microphysical Properties Over East Asia

A survey of the existing literature on in-situ measurements of cloud-precipitation microphysical properties has been undertaken over both East Asia and other regions. A database was established to contain microphysical properties for raindrop, cloud droplet, ice nuclei (IN), snow crystal, as well as the relationship between radar reflectivity (Z) and rainfall rate (R). From the datasets, dividing the data coverage into East Asia during the period of1960-2010and the other regions (which is defined as those include the Americas, Europe, Australia, and Africa) during the period of1940-2010. a statistical analysis has been performed. The results show that (1) various particles’total number concentrations vary greatly, but those occur only in certain scale distances;(2) the gamma-sized distribution has been widely used to describe the size distributions of cloud droplets in stratiform clouds, but fitted parameters have a wide range of variations;(3) both the exponential-and the gamma-sized distributions are suitable for representing the raindrops size distributions of the rains originated from stratiform clouds, and the gamma-sized distribution has been applied widely to describe RSDs of the rains originated from both convective and mixed (stratiform and cumuliform) clouds; and (4) the exponential-sized distribution is well adopted to represent the size distributions of ice crystals, snow crystals, and hailstones sampled at several locations.The properties over East Asia have been compared with those over the other regions. Both exponential-and gamma-size distributions have been applied to fit raindrop-size distributions over the world. The average intercept (N0) of exponential-size distributions is much smaller over East Asia than that over the other regions, and slope (λ) is slightly smaller. As for gamma-size distributions,the overall average value of intercept is much smaller over East Asia than that in the other regions, and the variation scope of parameters is narrower in East Asia than that in the other regions. Additionally, Most of the shape parameter (μ) are negative over East Asia, while positive μ appears frequently in the other regions. There is a higher total mean IN concentration (22.9L-1) in East Asia, compared with that (of2.7L-1) in the other regions. The average value of the intercept (N0) for snow-crystal size distributions over East Asia is much smaller than that in the other regions, and slope (λ) is not half as large as that in the other regions. The relation between Z and R suggests that the average Z is slightly larger in East Asia than that in the other regions for the rains originating from stratiform clouds with a same R, while Z is smaller in East Asia than that in the other regions for the rains originating from cumuliform clouds.The CloudSat satellite data during the period from June2006to April2011,are used to investigate cloud vertical profiles over the region of East Asia (20-50°N.80-120°E). with particular emphasis on comparing the profile of precipitative clouds with that of non-precipitative clouds, as well as the seasonal variations of these profiles. There are some obvious differences between the precipitative and non-precipitative cloud profiles. Generally, precipitative clouds mainly locate below8km with radar reflectivity in the range of-20-15dBz, and usually the clouds reach the ground; while non-precipitative clouds locate in the layers of4-12km with radar reflectivity between-28and0dBz. There are some different features among the liquid precipitative, solid precipitative, and possible drizzle precipitative cloud profiles. In precipitative clouds, radar reflectivity increases rapidly from11to7km in vertical, implying that condensation and collision-coalescence processes play a crucial role in the formation of large-size drops. The frequency distribution of temperature at-15℃is consistent with the highest frequency of radar reflectivity in solid precipitative clouds, which suggests that the temperatures near-15℃are conductive to deposition and accretion processes. The vertical distributions of liquid precipitative clouds differ from season to season with almost the same distributions in spring, summer and autumn as each other but the difference in winter mainly in the lower levels. However, the vertical distributions of solid precipitative clouds change from spring to winter with an alternate double and single high-frequency core, which is consistent with variations of the frequency distribution of temperature at-15℃. The vertical distributions of non-precipitative clouds show a little change with season. The observations also show that the precipitation events over East Asia are mostly related to deep convective clouds and nimbostratus clouds. These results are expected to be useful for future weather and climate model evaluation and improving microphysical parameterizations in a numerical model.Much progress of cloud microphysical parameterizaiton has been made since1970s. Generally, most microphysical parameterizaitons have been developed on the basis of Lin scheme and Rutledge-Hobbs scheme. A statistical analysis of the sensitivity tests results on microphysical parameterization over East Asia have been performed, and the results show that Lin scheme in the Weather Research and Forecasting (WRF) model performed well in simulations, and Goddard and Reisner schemes in the PSU/NCAR Mesoscale Model (MM5) simulated reasonably well on the whole. East Asia experiences the influence of the Asian monsoon, which has a significant impact on the regional weather and climate. Since the1960s, many numerical models have been used for operational weather forecasting and understanding the climate in East Asia (including developed locally and abroad). However, the microphysical processes used in these models were almost all copied from the numerical models developed abroad. As a result, the simulations show a general "degradation", that is, the results are poorer than those when they are used for the regions other than East Asia. One of the major reasons for the poor results is that the data collected over other regions do not represent conditions for the East Asia. To overcome the shortcoming, it is necessary to develop new parameterization schemes based on the microphysical properties over East Asia.A new double-moment bulk microphysics scheme predicting the number concentrations and mixing ratios of six hydrometeor species (cloud droplets, rain, cloud ice, snow, graupel, and hail) has developed and coupled with the Weather Research and Forecasting model (WRFv3.4). The gamma distribution function of the form N(D)=No11exp(-λD) is applied to represnet the size spectra of each hydrometeor category. In the new scheme, the shape parameter μ for cloud drop, rain and snow is a diagnostic variable, which is held constant in most schemes. To better understand cloud-precipitation microphysical properties over East Asia, we have carried out a statistical analysis for cloud-precipitation based on the in-situ measurement data during the period from1958to2010over East Asia, and the cloud-precipitation properties over East Asia have been compared with those over the other regions. As a result, new statistically based parameterizations are developed for parameters of particle-size distributions. Additionally, a new way to predict cloud droplet concentration (Nc) is developed based on the relationship between cloud liquid water content (LWC) and Nc, which is obtained from in situ measurements of135flights with2803records. Besides, the homogenous freezing of cloud droplets has been improved based on the statistical results of cloud vertical profile properties, which are obtained from the CloudSat satellite data during the period from June2006to April2011.The local heavy rain event occurring on24-25June2010in southern China was simulated using the new scheme and five sophisticated microphysics schemes in the WRF model. Results showed that the simulated24-h accumulated precipitations were generally agreed with observations.