排序方式： 共有60条查询结果，搜索用时 706 毫秒
31.
TAMDAR Observation Assimilation in WRF 3D-Var and Its Impact on Hurricane Ike (2008) Forecast 总被引：1，自引：0，他引：1 
下载免费PDF全文
下载免费PDF全文 This study evaluates the impact of atmospheric observations from the Tropospheric Airborne Meteorological Data Reporting (TAMDAR) observing system on numerical weather prediction of hurricane Ike (2008) using three-dimensional data assimilation system for the Weather Research and Forecast (WRF) model (WRF 3D-Var). The TAMDAR data assimilation capability is added to WRF 3D-Var by incorporating the TAMDAR observation operator and corresponding observation processing procedure. Two 6-h cycling data assimilation and forecast experiments are conducted. Track and intensity forecasts are verified against the best track data from the National Hurricane Center. The results show that, on average, assimilating TAMDAR observations has a positive impact on the forecasts of hurricane Ike. The TAMDAR data assimilation reduces the track errors by about 30 km for 72-h forecasts. Improvements in intensity forecasts are also seen after four 6-h data assimilation cycles. Diagnostics show that assimilation of TAMDAR data improves subtropical ridge and steering flow in regions along Ike’s track, resulting in better forecasts. 相似文献
32.
Existing satellite microwave algorithms for retrieving Sea Surface Temperature(Sst)and wind(SSW)are applicable primarily for non-raining cloudy conditions.With the launch of the Earth Observing System (EOS)Aqua satellite in 2002,the Advanced Microwave Scanning Radiometer(AMSR-E)onboard provides some unique measurements at lower frequencies which are sensitive to ocean surface parameters under ad-verse weather conditions.In this study,a new algorithm is developed to derive SST and SSW for hurricane predictions such as hurricane vortex analysis from the AMSR-E measurements at 6.925 and 10.65 GHz.In the algorithm,the effects of precipitation emission and scattering on the measurements are properly taken into account.The algorithm performances are evaluated with buoy measurements and aircraft dropsonde data.It is found that the root mean square (RMS) errors for SST and SSW are about 1.8K and 1.9m s(-1),respectively,when the results are compared with the buoy data over open oceans under precipitating clouds (e.g.,its liquid water path is larger than 0.5 mm),while they are 1.1 K for SST and 2.0 ms(-1)for SSW,respectively,when the retrievals are validated against the dropsonde measurements over warm oceans.These results indicate that our newly developed algorithm catl provide some critical surface information for trop-ical cycle predictions.Currently,this newly developed algorithm has been implemented into the hybrid variational scheme for the hurricane vortex analysis to provide predictions of SST and SSW fields. 相似文献
33.
Applications of AMSR-E Measurements for Tropical Cyclone Predictions Part Ⅰ： Retrieval of Sea Surface Temperature and Wind Speed 总被引：1，自引：0，他引：1
Existing satellite microwave algorithms for retrieving Sea Surface Temperature （SST） and Wind （SSW） are applicable primarily for non-raining cloudy conditions. With the launch of the Earth Observing System （EOS） Aqua satellite in 2002, the Advanced Microwave Scanning Radiometer （AMSRoE） onboard provides some unique measurements at lower frequencies which are sensitive to ocean surface parameters under adverse weather conditions. In this study, a new algorithm is developed to derive SST and SSW for hurricane predictions such as hurricane vortex analysis from the AMSRoE measurements at 6.925 and 10.65 GHz. In the algorithm, the effects of precipitation emission and scattering on the measurements are properly taken into account. The algorithm performances are evaluated with buoy measurements and aircraft dropsonde data. It is found that the root mean square （RMS） errors for SST and SSW are about 1.8 K and 1.9 m s^- 1, respectively, when the results are compared with the buoy data over open oceans under precipitating clouds （e.g., its liquid water path is larger than 0.5 mm）, while they are 1.1 K for SST and 2.0 m s^-1 for SSW, respectively, when the retrievals are validated against the dropsonde measurements over warm oceans. These results indicate that our newly developed algorithm can provide some critical surface information for tropical cycle predictions. Currently, this newly developed algorithm has been implemented into the hybrid variational scheme for the hurricane vortex analysis to provide predictions of SST and SSW fields. 相似文献
34.
35.
The climatic influence of sea-surface temperature (SST) on intensification is examined for North Atlantic hurricanes by averaging hourly intensity increases from best-track data over the period 1986–2013 in 4° by 4° latitude–longitude grid cells. Independent monthly SST data over the same period are averaged in the same cells. After removing cells with cold water or fast moving hurricanes, the SST effect on intensification, at the climate scale, is quantified by regressing intensification onto SST while controlling for average intensity. The regression is performed using a generalized linear model from a gamma family and a logarithmic link function. The model shows a statistically significant relationship, with higher intensification values associated with higher SST values. On average, mean intensification increases by 16% [(9,?20)% uncertainty interval] for every 1 °C increase in mean SST. A clustered region where the model underpredicts intensification is noted over the southeastern Caribbean Sea, perhaps related to the fresh water plume from the Orinoco River. 相似文献
36.
1998年台风与飓风异常成因分析 总被引：10，自引：4，他引：10
1998年,西北太平洋台风年发生频数创下14个的谷值,打破了建国以来1951年全年生成20个台风的最低纪录。而在同年,大西洋飓风发生数目却创下了14个的近年最高纪录。本文利用NCEP/NCAR再分析等资料,分析了台风发生与越赤道气流活动异常之间的关系。发现:1998年夏季(6~9月)东半球90 E～180 区间里越赤道气流明显地偏弱,而0～90 E区间里,特别是位于40～45 E的索马里急流处,越赤道气流极强,是造成1998年南海及西北太平洋台风发生数目特少的重要原因。而1998年大西洋飓风发生数比气候平均发生数目明显偏多以及当年强烈飓风造成重大灾害的主要原因,也正是由于1998年夏季40 W及75 W处越赤道气流异常强劲所引起的。 相似文献
37.
2005年全球重大天气气候事件概述 总被引：5，自引：3，他引：5
2005年，全球气候持续偏暖，是有记录以来第二暖年，仅次于最暖年1998年。年内，南亚地区遭受高温热浪袭击，欧洲中部和西部经历了极为严重的高温干旱，巴西北部亚马逊热带雨林遭遇了近60年来最严重的干旱。全球各地出现了不同程度的洪涝，此外，暴雨雪袭击了西亚、南亚北部、中亚、日本和中国的部分地区、美国和欧洲部分地区。2005年全球飓风（台风）灾害十分惨重。大西洋飓风为历史上最活跃的一年，其中飓风“卡特里娜”成为有记录以来影响美国最严重的飓风。西北太平洋台风活动虽较常年偏弱，但登陆中国的热带风暴和台风则数量多、强度强和灾害重。 相似文献
38.
The effects of storm-induced sea surface temperature (SST) cooling on hurricane intensity are investigated using a 5-day cloud-resolving simulation of Hurricane Bonnie (1998). Two sensitivity simulations are performed in which the storm-induced cooling is either ignored or shifted close to the modeled storm track. Results show marked sensitivity of the model-simulated storm intensity to the magnitude and relative position with respect to the hurricane track. It is shown that incorporation of the storm-induced cooling, with an average value of 1.3℃, causes a 25-hPa weakening of the hurricane, which is about 20 hPa per 1℃ change in SST. Shifting the SST cooling close to the storm track generates the weakest storm, accounting for about 47% reduction in the storm intensity. It is found that the storm intensity changes are well correlated with the air-sea temperature difference. The results have important implications for the use of coupled hurricane-ocean models for numerical prediction of tropical cyclones. 相似文献
39.
40.
Dependence of Hurricane Intensity and Structures on Vertical Resolution and Time-Step Size 总被引：5，自引：0，他引：5
In view of the growing interests in the explicit modeling of clouds and precipitation, the effects of varying vertical resolution and time-step sizes on the 72-h explicit simulation of Hurricane Andrew (1992) are studied using the Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) mesoscale model (i.e., MM5) with the finest grid size of 6 km. It is shown that changing vertical resolution and time-step size has significant effects on hurricane intensity and inner-core cloud/precipitation, but little impact on the hurricane track. In general, increasing vertical resolution tends to produce a deeper storm with lower central pressure and stronger three-dimensional winds, and more precipitation. Similar effects, but to a less extent, occur when the time-step size is reduced. It is found that increasing the low-level vertical resolution is more efficient in intensifying a hurricane, whereas changing the upper-level vertical resolution has little impact on the hurricane intensity. Moreover, the use of a thicker surface layer tends to produce higher maximum surface winds. It is concluded that the use of higher vertical resolution,a thin surface layer, and smaller time-step sizes, along with higher horizontal resolution, is desirable to model more realistically the intensity and inner-core structures and evolution of tropical storms as well as the other convectively driven weather systems. 相似文献