Shi Guangyu

The Impacts of Optical Properties on Radiative Forcing Due to Dust Aerosol

There are large uncertainties in the quantitative assessment of radiative effects due to atmospheric dust aerosol. The optical properties contribute much to those uncertainties. The authors perform several sensitivity experiments to estimate the impacts of optical characteristics on regional radiative forcing in this paper. The experiments involve in refractive indices, single scattering albedo, asymmetry factor and optical depth. An updated dataset of refractive indices representing East Asian dust and the one recommended by the World Meteorology Organization (WMO) are contrastively analyzed and used. A radiative transfer code for solar and thermal infrared radiation with detailed aerosol parameterization is employed. The strongest emphasis is on the refractive indices since other optical parameters strongly depend on it, and the authors found a strong sensitivity of radiative forcing on refractive indices. Studies show stronger scattering, weaker absorption and forward scattering of the East Asian dust particles at solar wavelengths, which leads to higher negative forcing, lower positive forcing and bigger net forcing at the top of the atmosphere (TOA) than that of the WMO dust model. It is also found that the TOA forcings resulting from these two dust models have opposite signs in certain regions, which implies the importance of accurate measurements of optical properties in the quantitative estimation of radiative forcing.

Numerical simulation of global temperature change during the 20th century with the IAP/LASG GOALS model

The IAP/LASG GOALS coupled model is used to simulate the climate change during the 20th century using historical greenhouse gases concentrations, the mass mixing ratio of sulfate aerosols simulated by a CTM model, and reconstruction of solar variability spanning the period 1900 to 1997. Four simulations, including a control simulation and three forcing simulations, are conducted. Comparison with the observational record for the period indicates that the three forcing experiments simulate reasonable temporal and spatial distributions of the temperature change. The global warming during the 20th century is caused mainly by increasing greenhouse gas concentration especially since the late 1980s; sulfate aerosols offset a portion of the global warming and the reduction of global temperature is up to about 0.11°C over the century; additionally, the effect of solar variability is not negligible in the simulation of climate change over the 20th century.The IAP/LASG GOALS coupled model is used to simulate the climate change during the 20th century using historical greenhouse gases concentrations, the mass mixing ratio of sulfate aerosols simulated by a CTM model, and reconstruction of solar variability spanning the period 1900 to 1997. Four simulations, including a control simulation and three forcing simulations, are conducted. Comparison with the observational record for the period indicates that the three forcing experiments simulate reasonable temporal and spatial distributions of the temperature change. The global warming during the 20th century is caused mainly by increasing greenhouse gas concentration especially since the late 1980s; sulfate aerosols offset a portion of the global warming and the reduction of global temperature is up to about 0.11°C over the century; additionally, the effect of solar variability is not negligible in the simulation of climate change over the 20th century.

Estimation of the Distribution of Global Anthropogenic Heat Flux

Abstract The radiance lights data in 2006 from the National Oceanic and Atmospheric Administration Air Force Defense Meteorological Satellite Program/Operational Linescan System (DMSP/OLS) and authoritative energy data distributed by the United State Energy Information Administration were applied to estimate the global distribution of anthropogenic heat flux. A strong linear relationship was found to exist between the anthropogenic heat flux and the DMSP/OLS radiance data. On a global scale, the average value of anthropogenic heat flux is approximately 0.03 W m–2 and 0.10 W m–2 for global land area. The results indicate that global anthropogenic heat flux was geographically concentrated and distributed, fundamentally correlating to the economical activities. The anthropogenic heat flux concentrated in the economically developed areas including East Asia, Europe, and eastern North America. The anthropogenic heat flux in the concentrated regions, including the northeastern United States, Central Europe, United Kingdom, Japan, India, and East and South China is much larger than global average level, reaching a large enough value that could affect regional climate. In the center of the concentrated area, the anthropogenic heat flux density may exceed 100 W m–2, according to the results of the model. In developing areas, including South America, Central and North China, India, East Europe, and Middle East, the anthropogenic heat flux can reach a level of more than 10 W m–2; however, the anthropogenic heat flux in a vast area, including Africa, Central and North Asia, and South America, is low. With the development of global economy and urban agglomerations, the effect on climate of anthropogenic heat is essential for the research of climate change.

Approximations of the Scattering Phase Functions of Particles

Based on anomalous diffraction theory and the modified Rayleigh-Debye approximation, a physically realistic model in bridging form is described to approximate the scattering phase function of particles. When compared with the exact method, the bridging technique reported here provides a reasonable approximation to the Mie results over a broader range of angles and size parameters, and it demonstrates the advantage of being computationally economic. In addition, the new phase function model can be essentially extended to other shapes and conveniently used in more complicated scattering and emission problems related to the solutions of the radiative transfer equations.

Satellite-derived primary productivity and its spatial and temporal variability in the China seas

The spatial and temporal variability of primary productivity in the China seas from 2003 to 2005 was estimated using a size-fractionated primary productivity model. Primary productivity estimated from satellite-derived data showed spatial and temporal variability. Annual averaged primary productivity levels were 564.39, 363.08, 536.47, 413.88, 195.77, and 100.09 gCm−2a−1 in the Bohai Sea, northern Yellow Sea (YS), southern YS, northern East China Sea (ECS), southern ECS, and South China Sea (SCS), respectively. Peaks of primary productivity appeared in spring (April–June) and fall (October and November) in the northern YS, southern YS, and southern ECS, while a single peak (June) appeared in the Bohai Sea and northern ECS. The SCS had two peaks in primary productivity, but these peaks occurred in winter (January) and summer (August), with the winter peak far higher than the summer peak. Monthly averaged primary productivity values from 2003 to 2005 in the Bohai Sea and southern YS were higher than those in the other four seas during most months, while those in the southern ECS and SCS were the lowest. Primary productivity in spring (March–June in the southern ECS and April–July in the other five areas) contributed approximately 41% on average to the annual primary productivity in all the study seas except the SCS. The largest interannual variability also occurred in spring (average standard deviation = 6.68), according to the satellite-derived estimates. The contribution during fall (October–January in the southern ECS and August–November in the other five areas) was approximately 33% on average; the primary productivity during this period also showed interannual variability. However, in the SCS, the winter (December–March) contribution was the highest (about 42%), while the spring (April–July) contribution was the lowest (28%). The SCS did share a feature with the other five areas: the larger the contribution, the larger the interannual variability. Spatial and temporal variability of satellite-derived ocean primary productivity may be influenced by physicochemical environmental conditions, such as the chlorophyll-a concentration, sea surface temperature, photosynthetically available radiation, the seasonally reversed monsoon, river discharge, upwelling, and the Kuroshio and coastal currents.

Correlation of Dust Storms in China with Chlorophyll a Concentration in the Yellow Sea between 1997-2007

Abstract Based on daily observation data at 222 meteorological stations in China, the characteristics of dust storms between 1997 and 2007 were examined. Next, the relationship between dust events and chlorophyll (Chl) a concentration in the Yellow Sea was investigated. There were six regions with high annual frequencies of dust storms. The seasonal distribution of dust storms showed spatiotemporal variation. The six regions with highest annual frequencies also exhibited high frequencies of dust storms in spring. Dust storms in most regions occurred in spring. Of all dust storms in China, sixty-five percent of all dust storms occurred during the spring. The area and frequency of dust storms were smaller in fall and winter than in spring and summer. A significant correlation was found between dust events and Chl a concentration in the Yellow Sea. High correlation regions included Qinghai-Xizang region, part of the Hexi Corridor, the western Inner Mongolia and Hetao Regions, and the Hunshandake Desert. The high correlation may be induced by the high ratio of dust storms in the abovementioned regions that arrive over the Yellow Sea, as inferred through a forward trajectory analysis; especially notable is dust transported at a lower altitude (< 3 km).

Assessment of Dust Aerosol Optical Depth and Shortwave Radiative Forcing over the Northwest Pacific Ocean in Spring Based on Satellite Observations

Abstract Dust aerosol optical depth (AOD) and its accompanying shortwave radiative forcing (RF) are usually simulated by numerical models. Here, by using 9 months of Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol product data in combination with Clouds and the Earths Radiant Energy System Single Scanner Footprint (CERES/SSF) data, dust AOD and its shortwave RF were estimated over the cloud—free north—West (NW) Pacific Ocean in the springs of 2004, 2005, and 2006. The results showed that in this region, the mean dust AOD and its shortwave RF were 0.10 and –5.51 W m-2, respectively. In order to validate the dust AOD derived by MODIS, results from the Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model were also used here. The correlation coefficient between the monthly averaged dust AOD derived by MODIS measurements and the model simulation results was approximately 0.53. Since the estimates of the dust AOD and its shortwave RF obtained in this study are based mainly on satellite data, they offer a good reference for numerical models.

Effect of HITRAN Database Improvement on Retrievals of Atmospheric Carbon Dioxide from Reflected Sunlight Spectra in the 1.61-μm Spectral Window

A large number of experimental and theoretical investigations of carbon dioxide (CO2) spectra have been conducted since the most recent update of the High-Resolution Transmission Molecular Absorption (HITRAN) database. To maintain optimal parameters, the HITRAN 2004 CO2 line list has been completely replaced by HITRAN 2008 data in the near-infrared region from 4300 cm−1 to 7000 cm−1. To examine the effect of this change on the retrieval of CO2 vertical column data from reflected sunlight spectra in the 1.61-µm spectral window, synthetic measurements for a given atmospheric state and instrument setup were generated and compared using radiative transfer model with the line-transition parameters from the HITRAN 2004 and 2008 databases. Simulated retrievals were then performed based on the optimal estimation retrieval theory. The results show that large systematic errors in atmospheric CO2 column retrievals were induced by the differences in the HITRAN laboratory line parameters in the 1.61-µm region. The retrieved CO2 columns were underestimated by >10 ppm using the HITRAN 2004 data, and improvements resulting from the use of the improved HITRAN database were more pronounced at a higher spectral resolution.

Detecting Aerosols over Land from Satellites by Measuring Far IR Radiation from the Earth-Atmospheric System

Abstract In this study, a special method is proposed for detecting aerosols over land by analyzing satellitemeasured far IR radiation at three channels, 8.7, 11.5, and 12.5µm. Sensitivity tests revealed that the behavioral features of radiative brightness temperatures (BTs) at these three channels with increasing optical depth are different among different types of aerosols. Analyzing how BTs and their differences, xBT (BT11.5-BT12.5) and yBT (BT8.7-BT11.5), behave with varying optical depth can help to qualitatively distinguish among aerosols and semi-quantitatively estimate their optical thicknesses. In addition, the authors found that the vertical density profile of aerosols has little impact on this method.