This study assesses the direct and indirect effects of natural and anthropogenic aerosols （e.g., black carbon and sulfate） over West and Central Africa during the West African monsoon （WAM） period （June-July-Aug...This study assesses the direct and indirect effects of natural and anthropogenic aerosols （e.g., black carbon and sulfate） over West and Central Africa during the West African monsoon （WAM） period （June-July-August）. We investigate the impacts of aerosols on the amount of cloudiness, the influences on the precipitation efficiency of clouds, and the associated radiative forcing （direct and indirect）. Our study includes the implementation of three new formulations of auto-conversion parameterization [namely, the Beheng （BH）, Tripoli and Cotton （TC） and Liu and Daum （R6） schemes] in RegCM4.4.1, besides the default model＇s auto-conversion scheme （Kessler）. Among the new schemes, BH reduces the precipitation wet bias by more than 50% over West Africa and achieves a bias reduction of around 25% over Central Africa. Results from detailed sensitivity experiments suggest a significant path forward in terms of addressing the long-standing issue of the characteristic wet bias in RegCM. In terms of aerosol-induced radiative forcing, the impact of the various schemes is found to vary considerably （ranging from -5 to -25 W m-2）.展开更多
In recent years, the upper air radiosounding system based on GPS （global positioning system） is used as an effective method resulting to improving observation accuracy and helping in simplification of the ground equ...In recent years, the upper air radiosounding system based on GPS （global positioning system） is used as an effective method resulting to improving observation accuracy and helping in simplification of the ground equipment. GPS is used to calculate the pressure and wind speed and direction. The NAVSTAR GPS has been developed by the Department of Defense of the United States, and the main purpose is to provide the military forces of the USA and its allies with a means to accurately determine their position, velocity and time, anywhere on the earth, at any time. Europe is now developing its own GPS, known as Galileo, which is independent of the USA GPS. As a result, many countries now are developing their own GPS system like Russia （GLONASS）, China （Compass）, India, and Japan. As a direct result, we can face the fact that each and every country will have its own GPS system and finally we come up with a crowded space. The INS （inertial navigation system） is a system that, once initialized （by acquiring the initial position, velocity, and orientation information）, becomes an autonomous navigation system providing 3-D position, velocity, and attitude information. So upper air observation can take advantage of this emerging technology by using this stand alone system （INS） in measuring wind speed and direction as well as measuring the altitude we can calculate the pressure.展开更多
文摘This study assesses the direct and indirect effects of natural and anthropogenic aerosols （e.g., black carbon and sulfate） over West and Central Africa during the West African monsoon （WAM） period （June-July-August）. We investigate the impacts of aerosols on the amount of cloudiness, the influences on the precipitation efficiency of clouds, and the associated radiative forcing （direct and indirect）. Our study includes the implementation of three new formulations of auto-conversion parameterization [namely, the Beheng （BH）, Tripoli and Cotton （TC） and Liu and Daum （R6） schemes] in RegCM4.4.1, besides the default model＇s auto-conversion scheme （Kessler）. Among the new schemes, BH reduces the precipitation wet bias by more than 50% over West Africa and achieves a bias reduction of around 25% over Central Africa. Results from detailed sensitivity experiments suggest a significant path forward in terms of addressing the long-standing issue of the characteristic wet bias in RegCM. In terms of aerosol-induced radiative forcing, the impact of the various schemes is found to vary considerably （ranging from -5 to -25 W m-2）.
文摘In recent years, the upper air radiosounding system based on GPS （global positioning system） is used as an effective method resulting to improving observation accuracy and helping in simplification of the ground equipment. GPS is used to calculate the pressure and wind speed and direction. The NAVSTAR GPS has been developed by the Department of Defense of the United States, and the main purpose is to provide the military forces of the USA and its allies with a means to accurately determine their position, velocity and time, anywhere on the earth, at any time. Europe is now developing its own GPS, known as Galileo, which is independent of the USA GPS. As a result, many countries now are developing their own GPS system like Russia （GLONASS）, China （Compass）, India, and Japan. As a direct result, we can face the fact that each and every country will have its own GPS system and finally we come up with a crowded space. The INS （inertial navigation system） is a system that, once initialized （by acquiring the initial position, velocity, and orientation information）, becomes an autonomous navigation system providing 3-D position, velocity, and attitude information. So upper air observation can take advantage of this emerging technology by using this stand alone system （INS） in measuring wind speed and direction as well as measuring the altitude we can calculate the pressure.
