The data from CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite was used to
analyze the aerosol micro-physical properties over Beijing and surrounding area during haze periods from 2007 to 2008
in this paper. The results showed as follows. The values of TABC (total attenuated backscatter coefficient) for aerosols
accounted for about 25% with varying altitudes. The aerosol scattering ability little changed from 0-4 km, showing that
the aerosol layer evenly distribute. At different altitude ranges (0-1, 1-2, 2-3 and 3-4 km above ground level), values of
TABC almost concentrate in the range of 2.5×10-3 -4.5×10-3 km-1.sr-1. In spring, summer and winter, aerosol scattering
has the similar variation, with the maximum of TABC ranging from 3.5×10-3 km-1.sr-1 to 4.5×10-3 km-1.sr-1, while the
maximum of TABC in autumn is from 1.5×10-3 km-1.sr-1 to 2.5×10-3 km-1.sr-1. Aerosol shape and size are characterized by
VDR (volume depolarization ratio) and TACR (total attenuated color ratio). Aerosols with VDR greater than 10% were
more than the ones with VDR less than 10% at the same altitude range. Notably, aerosols with smaller VDR (0-10%)
appeared more frequently in autumn than those in the other three seasons. For each altitude range, aerosols with TACR
ranging from 0-0.2 contributed much more than those with TACR ranging from 1.8-2.0. The size of aerosols in summer
was the largest and that in autumn was the smallest in middle and lower troposphere.
The Model of Atmospheric Transport and Chemistry (MATCH) developed by the National Center for Atmospheric
Research (NCAR) is used to calculate the aerosol optical depth (AOD) over China in 2006, with the updated emission
inventory of Streets (2007) and NCEP/NCAR reanalysis data as its inputs. The simulation results of AOD are then
compared with observational data from Chinese Sun Hazemeter Network (CSHNET), Aerosol Robotics Network
(AERONET) at more than 23 stations over China, and Moderate Resolution Imaging Spectroradiometer (MODIS)
satellite data. The model reproduces most of the prominent features in the CSHNET observation data with an overall
agreement within a factor of 2. However, there exist large differences between the simulation and the MODIS data, due
to the large uncertainties in the model and the satellite data.
A comparative study is made for black carbon aerosol (BC) in this text based on BC and PM10 observations as well as
their air pollution indices during January-December 2006 in Beijing and Lhasa regions. BC concentration is
considerably higher in Beijing than in Lhasa because of anthropogenic activities, with an annual mean of 9.3 μg/m3
versus 3 μg/m3 from the standard channel of 880 nm (below is the same). It is higher in winter and lower in summer for
both of the regions, with the value in a heating season being more than twice as high as in non-heating season in Beijing
area. The highest monthly means of 16.8 μg/m3 vs 5.5 μg/m3 occur in January in Beijing and Lhasa regions, respectively; whereas the lowest values of 4.5 μg/m3 vs 2.2 μg/m3 are in July. The daily higher values of BC in Beijing start from 1600 BST (Beijing standard time) and maintain until 0700 BST of the next day, with keeping lower values during other
daytime hours, especially around the noon. The daily maximum and minimum values of 30 μg/m3 and 1.4 μg/m3 happens in December and April in Beijing in 2006, respectively. Generally, BC emissions in Lhasa are much smaller than in
Beijing, with relative high values observed in the morning and afternoon; the 2006 daily maximum and minimum of 12.4
μg/m3 and 0.8 μg/m3 appear in the December and the March, respectively. The BC in Lhasa mainly comes from the local emission from vehicles to the atmosphere.
Better understanding the dynamics of the East Asian monsoon system is essential to address its climate variability and predictability. Regional climate models are useful tools for this endeavor, but require a rigorous evaluation to first establish a suite of physical parameterizations that best simulate observations. To this end, the present study focuses on the CWRF (Climate extension of WRF) simulation of the 1998 summer flood over east China and its sensitivity to cumulus parameterizations on CWRF performance. The CWRF using the Kain-Fritsch and Grell-Devenyi cumulus schemes both capture the observed major characteristics of geographic distributions and daily variations of precipitation, indicating a high credibility in downscaling the monsoon. Important regional differences, however, are simulated by the two schemes. The Kain-Fritsch scheme produces the better precipitation patterns with smaller root-mean-square errors and higher temporal correlation coefficients, while overestimating the magnitude and coverage. In contrast, the Grell-Devenyi ensemble scheme, using equal weights on all closure members, overall underestimates rainfall amount, suggesting for future improvement with varying weights depending on climate regimes.
The capability of the Climate extension of the Weather Research and Forecasting (CWRF) model in simulating the 1991 and 1998 summer floods in China is evaluated with 4-month continuous integrations as driven by the NCEP/NCAR observational reanalysis. It is shown that CWRF has a pronounced downscaling skill, capturing the key characteristics in the spatial patterns and temporal evolutions of precipitation in both severe anomalous monsoon cases. The result gives a high perspective for future CWRF applications in understanding and predicting China monsoon variability.
Band division is an important basis in radiative calculations, and the configuration of band divisions for various research purposes directly influences the accuracy and speed of radiative transfer computations. We explore four band-division schemes and their impacts on computed radiative fluxes and cooling rates. We explain that discrepancies in solar radiation at the surface that exist between radiation models and observations under clear-sky conditions arise partly from ignoring minor gases and weak absorption bands for major gases.
China is a country with complex topography, land surface conditions, coastlines with the world highest plateau in its west and the largest ocean at its east, and with large contribution from mesoscale phenomena, such as the mei-yu frontal systems and tropical storms. To study the regional climate in such a region, a highly resolved regional climate model (RegCM) has been recently developed at the International Pacific Research Center (IPRC). The distinct features of this model include direct feedback of cumulus detrained cloud ice and cloud water into the grid-resolved quantities; the effect of cloud buoyancy on turbulence production with mixed-ice phase clouds; an explicit coupling between the cloud microphysics and radiation via cloud properties; an explicit coupling between land surface and radiation via surface albedo, direct and diffuse radiation fluxes; and the effect of frictionally generated dissipative heating. The performance of RegCM3 is demonstrated by its simulation of the 2003 summer extreme climate event over the whole China region including Tibetan Plateau. There have not had so many studies about this region on this regard. With the use of the NCEP Reanalysis 2 data provided by the NOAA-CIRES Climate Diagnostic Center, Boulder, Colorado, USA, from their Web site at http://www.cdc.noaa.gov/, which is available at 6hr intervals with a resolution of 2.5°×2.5°, as both the initial and lateral boundary conditions, the model was integrated from 1 May to 31 August 2003 with a resolution of 60km×60km covering the area of 15°-55°N, 70°-140°E. It is demonstrated that the RegCM3 has a pronounced rainfall downscaling scale, producing more realistic regional details and overall smaller biases than the driving reanalysis data. The model simulated realistically not only the temporal evolution of the area-averaged precipitation and the monthly mean precipitation spatial pattern but also the daily precipitation intensity distribution.
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