Spatial And Temporal Characteristics Of The Tibetan Plateau Aerosol Radiative Forcing And Climate Effect Of Numerical Simulation

We reviewed and introduced the work about aerosol radiative forcing and climate response in this paper at first. Then We analyzed the geographical and temporal distribution of aerosol over Tibetan Plateau by using the monthly mean SAGE II (Stratospheric Aerosol and Gas Expenment II) data, which dated from January 1985 to December 1993. The result is as follows: (1) Stratospheric aerosol optical depth has an oscillation in the four quarters. It means that aerosol optical depth becomes the thickest in Winter, and a little thinner in Spring, and the thinnest in Summer, and a little thicker in Autumn, and then the thickest in Winter too. We have found that the oscillation is caused by the vibration of tropopause in different seasons. (2) Stratospheric aerosol comes mainly from sprays of the volcano. Aerosol optical depth in stratosphere over Tibetan Plateau became 10 times of itself after eruption of Mount Pinatubo in Philippines. (3) The characteristic of aerosol vertical distribution over Tibetan Plateau is that there is a extremely high value at the height of 70hPa. The more interesting thing is that the extremely high value can oscillate between the height of 5OhPa and l00hPa. We have verified that the oscillation is a unique characteristic over Tibetan Plateau by comparing it with South China and Northwest China. Based on the analysis of SAGE II data, we substitute the uniform background boundary layer aerosol with parameterized aerosol among each layer in radiative scheme of CCM3 .Then the radiative forcing and regional climate response over Tibetan Plateau of the change of aerosol were investigated. It is found that: (1) The radiative forcing is positive because the parameterized aerosol optical depth is less than 0.14 which is the optical depth of the uniform background boundary layer aerosol. They are 0?W/m2 in January and 0-4W/rn2 in April and less than 3W/rn2 in July and 3?W/rn2 in October. (2) The earth抯 surface temperature rises about 0.1-0.2K in October which is the biggest increasing magnitude, and 0.01-0.02K in July which is the smallest one. It rises about 0.05-0.1K in January and April. (3) Air temperature near the earth and at the height of 500hPa rise too. They rise less than the magnitude of the earth抯 surface temperature, but they have the same trend in four different months.