Rain cells or convective rain,the dominant form of rain in the tropics and subtropics,can be easy detected by satellite Synthetic Aperture Radar（SAR） images with high horizontal resolution.The footprints of rain cel...Rain cells or convective rain,the dominant form of rain in the tropics and subtropics,can be easy detected by satellite Synthetic Aperture Radar（SAR） images with high horizontal resolution.The footprints of rain cells on SAR images are caused by the scattering and attenuation of the rain drops,as well as the downward airflow.In this study,we extract sea surface wind field and its structure caused by rain cells by using a RADARSAT-2 SAR image with a spatial resolution of 100 m for case study.We extract the sea surface wind speeds from SAR image by using CMOD4 geophysical model function with outside wind directions of NCEP final operational global analysis data,Advance Scatterometer（ASCAT） onboard European Met Op-A satellite and microwave scatterometer onboard Chinese HY-2 satellite,respectively.The root-mean-square errors（RMSE） of these SAR wind speeds,validated against NCEP,ASCAT and HY-2,are 1.48 m/s,1.64 m/s and 2.14 m/s,respectively.Circular signature patterns with brighter on one side and darker on the opposite side on SAR image are interpreted as the sea surface wind speed（or sea surface roughness） variety caused by downdraft associated with rain cells.The wind speeds taken from the transect profile which superposes to the wind ambient vectors and goes through the center of the circular footprint of rain cell can be fitted as a cosine or sine curve in high linear correlation with the values of no less than 0.80.The background wind speed,the wind speed caused by rain cell and the diameter of footprint of the rain cell with kilometers or tens of kilometers can be acquired by fitting curve.Eight cases interpreted and analyzed in this study all show the same conclusion.展开更多
Rain cells are the most elementary unit of precipitation system in nature.In this study,fundamental geometric and physical characteristics of rain cells over tropical land and ocean areas are investigated by using 15-...Rain cells are the most elementary unit of precipitation system in nature.In this study,fundamental geometric and physical characteristics of rain cells over tropical land and ocean areas are investigated by using 15-yr measurements of the Tropical Rainfall Measuring Mission(TRMM)Precipitation Radar(PR).The rain cells are identified with a minimum bounding rectangle(MBR)method.The results indicate that about 50%of rain cells occur at length of about 20 km and width of 15 km.The proportion of rain cells with length>200 km and width>100 km is less than1%.There is a a log-linear relationship between the mean length and width of rain cells.Usually,for the same horizontal geometric parameters,rain cells tend to be square horizontally and lanky vertically over land,while vertically squatty over ocean.The rainfall intensity of rain cells varies from 0.4 to 10 mm h-1 over land to 0.4–8 mm h-1 over ocean.Statistical results indicate that the occurrence frequency of rain cells decreases as the areal fraction of convective precipitation in rain cells increases,while such frequency remains almost invariant when the areal fraction of stratiform precipitation varies from 10%to 80%.The relationship between physical and geometric parameters of rain cells shows that the mean rain rate of rain cells is more frequently associated with the increase of their area,with the increasing rate over land greater than that over ocean.The results also illustrate that heavy convective rain rate prefers to occur in larger rain cells over land while heavy stratiform rain rate tends to appear in larger rain cells over ocean.For the same size of rain cells,the areal fraction and the contribution of convective precipitation are about10%–15%higher over land than over ocean.展开更多
Pursuit of energy-harvesting or-storage materials to realize outstanding electricity output from nature has been regarded as a promising strategy to resolve the energy-lack issue in the future. Among them,the solar ce...Pursuit of energy-harvesting or-storage materials to realize outstanding electricity output from nature has been regarded as a promising strategy to resolve the energy-lack issue in the future. Among them,the solar cell as a solar-to-electrical conversion device has been attracted enormous interest to improve the efficiency. However, the ability to generate electricity is highly dependent on the weather conditions,in other words, there is nearly zero power output in dark-light conditions, such as rainy, cloudy, and night, lowering the monolithic power generation capacity. Here, we present a bifunctional polyaniline film via chemical bath deposition, which can harvest energy from the rain, yielding an induced current of 2.57 μA and voltage of 65.5 μV under the stimulus of real raindrop. When incorporating the functional PANi film into the traditional dye sensitized solar cell as a counter electrode, the hybridized photovoltaic can experimentally realize the enhanced output power via harvesting energy from rainy and sunny days. The current work may show a new path for development of advanced solar cells in the future.展开更多
基金The Joint Foundation of National Natural Science Foundation of China and the Marine Science Center of Shandong Province under contract No.U1406404the National Natural Science Foundation of China under contract Nos 41506206,41306186 and41476152+1 种基金the Global Change and Air-Sea Interaction Project of China under contract No.GASI-03-03-01-01the Open funds of State Key Laboratory of Satellite Ocean Environment Dynamics under contract No.SOED1411
文摘Rain cells or convective rain,the dominant form of rain in the tropics and subtropics,can be easy detected by satellite Synthetic Aperture Radar（SAR） images with high horizontal resolution.The footprints of rain cells on SAR images are caused by the scattering and attenuation of the rain drops,as well as the downward airflow.In this study,we extract sea surface wind field and its structure caused by rain cells by using a RADARSAT-2 SAR image with a spatial resolution of 100 m for case study.We extract the sea surface wind speeds from SAR image by using CMOD4 geophysical model function with outside wind directions of NCEP final operational global analysis data,Advance Scatterometer（ASCAT） onboard European Met Op-A satellite and microwave scatterometer onboard Chinese HY-2 satellite,respectively.The root-mean-square errors（RMSE） of these SAR wind speeds,validated against NCEP,ASCAT and HY-2,are 1.48 m/s,1.64 m/s and 2.14 m/s,respectively.Circular signature patterns with brighter on one side and darker on the opposite side on SAR image are interpreted as the sea surface wind speed（or sea surface roughness） variety caused by downdraft associated with rain cells.The wind speeds taken from the transect profile which superposes to the wind ambient vectors and goes through the center of the circular footprint of rain cell can be fitted as a cosine or sine curve in high linear correlation with the values of no less than 0.80.The background wind speed,the wind speed caused by rain cell and the diameter of footprint of the rain cell with kilometers or tens of kilometers can be acquired by fitting curve.Eight cases interpreted and analyzed in this study all show the same conclusion.
基金Supported by the National Natural Science Foundation of China(91837310 and 41675041)National Key R&D Program of China(2018YFC1507200 and 2017YFC1501402)+3 种基金Key Research and Development Projects in Anhui Province(201904a07020099)Third Tibetan Plateau Scientific Experiment Observations for Boundary Layer and Troposphere(GYHY201406001)Monitoring and Modelling Climate Change in WaterEnergy and Carbon Cycles in the Pan-Third Pole Environment in the Framework of the European Space Agency and Ministry of Science and Technology of the People’s Republic of China(ID58516)。
文摘Rain cells are the most elementary unit of precipitation system in nature.In this study,fundamental geometric and physical characteristics of rain cells over tropical land and ocean areas are investigated by using 15-yr measurements of the Tropical Rainfall Measuring Mission(TRMM)Precipitation Radar(PR).The rain cells are identified with a minimum bounding rectangle(MBR)method.The results indicate that about 50%of rain cells occur at length of about 20 km and width of 15 km.The proportion of rain cells with length>200 km and width>100 km is less than1%.There is a a log-linear relationship between the mean length and width of rain cells.Usually,for the same horizontal geometric parameters,rain cells tend to be square horizontally and lanky vertically over land,while vertically squatty over ocean.The rainfall intensity of rain cells varies from 0.4 to 10 mm h-1 over land to 0.4–8 mm h-1 over ocean.Statistical results indicate that the occurrence frequency of rain cells decreases as the areal fraction of convective precipitation in rain cells increases,while such frequency remains almost invariant when the areal fraction of stratiform precipitation varies from 10%to 80%.The relationship between physical and geometric parameters of rain cells shows that the mean rain rate of rain cells is more frequently associated with the increase of their area,with the increasing rate over land greater than that over ocean.The results also illustrate that heavy convective rain rate prefers to occur in larger rain cells over land while heavy stratiform rain rate tends to appear in larger rain cells over ocean.For the same size of rain cells,the areal fraction and the contribution of convective precipitation are about10%–15%higher over land than over ocean.
基金financial support from the National Natural Science Foundation of China (61774139, 21503202 and61604143)Shandong Provincial Natural Science Foundation (ZR2015EM024)the Fundamental Research Funds for the Central Universities (201564002, 201762018)
文摘Pursuit of energy-harvesting or-storage materials to realize outstanding electricity output from nature has been regarded as a promising strategy to resolve the energy-lack issue in the future. Among them,the solar cell as a solar-to-electrical conversion device has been attracted enormous interest to improve the efficiency. However, the ability to generate electricity is highly dependent on the weather conditions,in other words, there is nearly zero power output in dark-light conditions, such as rainy, cloudy, and night, lowering the monolithic power generation capacity. Here, we present a bifunctional polyaniline film via chemical bath deposition, which can harvest energy from the rain, yielding an induced current of 2.57 μA and voltage of 65.5 μV under the stimulus of real raindrop. When incorporating the functional PANi film into the traditional dye sensitized solar cell as a counter electrode, the hybridized photovoltaic can experimentally realize the enhanced output power via harvesting energy from rainy and sunny days. The current work may show a new path for development of advanced solar cells in the future.
