Wave forecast in the Atlantic Ocean using a double-stage ConvLSTM network          下载免费PDF全文

《大气和海洋科学快报》2023,16(4):100347

Accurate forecasting of ocean waves is of great importance to the safety of marine transportation. Despite wave forecasts having been improved, the current level of prediction skill is still far from satisfactory. Here, the authors propose a new physically informed deep learning model, named Double-stage ConvLSTM (D-ConvLSTM), to improve wave forecasts in the Atlantic Ocean. The waves in the next three consecutive days are predicted by feeding the deep learning model with the observed wave conditions in the preceding two days and the simultaneous ECMWF Reanalysis v5 (ERA5) wind forcing during the forecast period. The prediction skill of the d-ConvLSTM model was compared with that of two other forecasting methods—namely, the wave persistence forecast and the original ConvLSTM model. The results showed an increasing prediction error with the forecast lead time when the forecasts were evaluated using ERA5 reanalysis data. The d-ConvLSTM model outperformed the other two models in terms of wave prediction accuracy, with a root-mean-square error of lower than 0.4 m and an anomaly correlation coefficient skill of ∼0.80 at lead times of up to three days. In addition, a similar prediction was generated when the wind forcing was replaced by the IFS forecasted wind, suggesting that the d-ConvLSTM model is comparable to the Wave Model of European Centre for Medium-Range Weather Forecasts (ECMWF-WAM), but more economical and time-saving.摘要海浪预报对海上运输安全至关重要. 本研究提出了一种涵盖物理信息的深度学习模型Double-stage ConvLSTM (D-ConvLSTM) 以改进大西洋的海浪预报. 将D-ConvLSTM模型与海浪持续性预测和原始ConvLSTM模型的预测技巧进行对比. 结果表明, 预测误差随着预测时长的增加而增加. D-ConvLSTM模型在预测准确度方面优于前二者, 且第三天预测的均方根误差低于0.4 m, 距平相关系数约在0.8. 此外, 当使用IFS预测风替代再分析风时, 能够产生相似的预测效果. 这表明D-ConvLSTM模型的预测能力能够与ECMWF-WAM模式相当, 且更节省计算资源和时间.  相似文献   

STUDY ON THE GENESIS OF ASYMMETRICAL DISTRIBUTION CHARACTERISTICS OF PRECIPITATION ASSOCIATED WITH THE TYPHOON HAITANG (2005) FROM THE VIEW OF ATMOSPHERIC FACTOR     

岳彩军  曹钰  顾问  谈建国  李小凡 《热带气象学报(英文版)》2016,22(3):265-276

The distribution of precipitation field from the typhoon Haitang (2005) during its landing on Fujian province shows obvious asymmetric feature. Based on the NCEP/NCAR FNL (Final Analysis) data, this study reveals the contributions of atmospheric factor to the asymmetrical distribution characteristics of precipitation associated with the typhoon, through the analysis of water vapor condition, vertical ascending motion condition, the calculation of the dry Q vector and its decomposition, and adiabatic heating in the air column of 1000hPa -600hPa (lower atmosphere) and 500hPa-100hPa (upper atmosphere). The results are as follows: (1) In the lower atmosphere, the humidity on both sides of typhoon path can be equivalent, while it is more wet on the right side than left in the upper atmosphere, which obviously presents asymmetric distribution characteristics. (2) Both range and intensity of the vertical motion on the right side are wider and stronger than counterparts on the left side no matter in the lower or upper atmosphere. (3) In the upper atmosphere, forcing role of atmosphere in vertical upward motion on the right side of typhoon path is the same as that on the left, while it is significantly different in the lower atmosphere, which is significantly broader in scope and stronger in the intensity, along with obvious asymmetric distribution characteristics. In addition, the further analysis of the Q vector decomposition indicates that the forcing effect of mesoscale weather systems on vertical upward motion is stronger than that of large scale weather systems in the lower atmosphere. (4) The adiabatic heating always exists on both lower and upper atmosphere, and the range and intensity of the adiabatic heating forcing showed asymmetric distribution on both lower and upper atmosphere. (5) In a summary, the upper atmosphere humidity conditions, the forcing role of lower atmosphere in vertical upward motion, especially, to mesoscale weather system, and adiabatic heating in the lower atmosphere, all show similar asymmetric distribution characteristics to that of precipitation field from the typhoon Haitang (2005), that is to say, the atmospheric factors as mentioned above are all contributed to genesis of the asymmetric distribution characteristics of precipitation.  相似文献   

Comparison of sampling strategies for object-based classification of urban vegetation from Very High Resolution satellite images     

《International Journal of Applied Earth Observation and Geoinformation》2016

Vegetation monitoring is becoming a major issue in the urban environment due to the services they procure and necessitates an accurate and up to date mapping. Very High Resolution satellite images enable a detailed mapping of the urban tree and herbaceous vegetation. Several supervised classifications with statistical learning techniques have provided good results for the detection of urban vegetation but necessitate a large amount of training data. In this context, this study proposes to investigate the performances of different sampling strategies in order to reduce the number of examples needed. Two windows based active learning algorithms from state-of-art are compared to a classical stratified random sampling and a third combining active learning and stratified strategies is proposed. The efficiency of these strategies is evaluated on two medium size French cities, Strasbourg and Rennes, associated to different datasets. Results demonstrate that classical stratified random sampling can in some cases be just as effective as active learning methods and that it should be used more frequently to evaluate new active learning methods. Moreover, the active learning strategies proposed in this work enables to reduce the computational runtime by selecting multiple windows at each iteration without increasing the number of windows needed.  相似文献   

基于MODIS热红外数据的渤海海冰厚度反演   总被引：3，自引：1，他引：2  

曾韬  石立坚  MARKO Makynen  程斌  邹巨洪  张治平 《海洋学报(英文版)》2016,35(7):96-104

Level ice thickness distribution pattern in the Bohai Sea in the winter of 2009–2010 was investigated in this paper using MODIS night-time thermal infrared imagery.The cloud cover in the imagery was masked out manually.Level ice thickness was calculated using MODIS ice surface temperature and an ice surface heat balance equation.Weather forcing data was from the European Centre for Medium-Range Weather Forecasts(ECMWF) analyses.The retrieved ice thickness agreed reasonable well with in situ observations from two off-shore oil platforms.The overall bias and the root mean square error of the MODIS ice thickness are –1.4 cm and 3.9 cm,respectively.The MODIS results under cold conditions(air temperature –10°C) also agree with the estimated ice growth from Lebedev and Zubov models.The MODIS ice thickness is sensitive to the changes of the sea ice and air temperature,in particular when the sea ice is relatively thin.It is less sensitive to the wind speed.Our method is feasible for the Bohai Sea operational ice thickness analyses during cold freezing seasons.  相似文献   

西藏高原土壤水分遥感监测方法研究          下载免费PDF全文

除多  次仁多吉  德吉央宗 《高原山地气象研究》2016,36(2):1-7

土壤水分是植物生长、发育的必要条件,是研究农牧业干旱程度的重要指标,监测土壤水分对农业、旱情、气候等具有重要意义。本研究分析了西藏高原实测土壤湿度与同期MODIS植被供水指数和波段7反射率之间的关系。结果表明,MODIS第7波段单窗算法是较为有效和简便的西藏高原土壤水分监测方法,对高原中部植被生长季基于MODIS波段7的二次多项式监测模型较好,而对整个高原非生长季三次多项式监测模型效果较好,MODIS第7波段同样可以用于高原农田土壤湿度的遥感监测。   相似文献   

LAPS上海本地化及其在局地对流天气中的应用研究     

唐玉琪  刘红亚  岳彩军  顾问 《气象科学》2019,39(1):50-61

本文首先基于地面自动站、探空、雷达和卫星资料,开展局地分析预报系统(Local Analysis and Prediction System,LAPS)上海本地化研究,并结合2010—2014年夏季6个局地对流天气个例对其性能进行检验评估。结果表明:雷达径向风资料对LAPS风速分析影响较大,使分析场风速廓线与探空廓线的均方根误差缩小约7.66%;风云卫星资料能够改善LAPS温度和相对湿度,使分析场温度、相对湿度廓线与探空廓线的均方根误差分别缩小约9.09%和14.01%;探空气球飘移对本文LAPS分析场检验影响不明显。进一步将LAPS分析场用于2011年8月13日、2014年8月4日两次局地对流个例分析表明:LAPS高时空分辨率的分析场能够反映中小尺度天气系统的时空变化,在天气尺度背景并不十分有利于对流生成的情况下,热岛、海陆风环流的形成和持续对上海夏季局地对流天气的发生和发展起到关键作用。  相似文献   

The occurrence of the typical mesoscale convective system with a flood-producing storm in the wet season over the Greater Jakarta area     

《Dynamics of Atmospheres and Oceans》2021

A complex convective cloud with a horizontal scale area of more than 100 km, known as the mesoscale convective system (MCS), is important to the study as it brings heavy rainfall from its activity. The analysis of MCS with the flood-producing storm on the Indonesian Maritime Continent (IMC) receives less attention. The purpose of this study is to identify and evaluate the temporal variability of the MCS to the frequency of flood-producing storms in Greater Jakarta (GJ) during the 2013–2015 wet season. The image data of Multi-functional Transport Satellite (MTSAT) -1R, which represents an equivalent blackbody temperature (TBB), and the tracking algorithm “Grab ‘em Tag ‘em Graph ‘em” (GTG) were used to detect the events of MCS. We also used a rainfall graph in this analysis to measure rainfall threshold values in order to classify flood-producing storms. The results show that MCS around GJ has typical characteristics of tropical belt regions. There is a small TBB scale (maximum size ≥13,000 km²) distinguished by a deep cloud up to 14 km in height. Through the active effects of monsoon and ITCZ, the land-breeze and/or sea-breeze circulations that contribute to MCS growth are triggered. However, about 32 percent of the MCS contributed to the flood-producing storm around the GJ region.  相似文献   

FY-3A微波资料偏差订正及台风路径预报应用   总被引：2，自引：0，他引：2       下载免费PDF全文

杜明斌  杨引明  杨玉华  张洁  朱雪松 《应用气象学报》2012,23(1):89-95

我国极轨气象卫星FY-3A大大增强了对地球系统的综合探测能力,而偏差订正对卫星资料的应用非常必要。试验中FY-3A卫星微波资料的偏差订正方案是在Harris等的TOVS辐射资料偏差订正经验方法的基础上结合WRF-3DVAR系统发展的,偏差订正后微波资料各通道拟合结果基本位于主对角线上,大多数卫星观测数据与观测算子利用背景场计算的亮温值分布趋于合理,偏差得到很大程度的降低。偏差订正后,利用数值模式直接同化FY-3A气象卫星微波资料,通过对2008年和2009年的4个台风进行预报评估表明:同化FY-3A气象卫星资料后路径预报能力提高明显,尤其是36 h后路径预报结果;同化FY-3A气象卫星微波资料后台风预报路径误差平均降低20%,而只同化常规资料路径误差仅仅降低了4%。  相似文献   

中国地区地磁正常场模型研究   总被引：2，自引：0，他引：2  

冯彦  安振昌  孙涵  毛飞 《地球科学进展》2010,25(7):723-729

基于2000年中国地区的实测地磁3分量数据,分别选用Taylor模型和第四代地磁场综合模型--CM4计算并绘制出正常场分布图.由于2种正常场分布较为相似,为了进一步比较研究,分别将实测值减去2种正常场模型值以得到2种磁异常值,并利用曲面Spline模型绘制各地磁分量磁异常图,结果显示:2种异常图分布基本一致,以CM4模型作为正常场与国界外的地磁分布结合得较好,适合进行大尺度的磁场研究,计算的磁异常分布在国内以负异常为主;以Taylor模型作为正常场适合进行局部区域的磁场研究,获得的磁异常图正负分布较为均匀、合理.  相似文献   

Temporal and spatial variations of high-impact weather events in China during 1959–2014     

Shi  Jun  Wen  Kangmin  Cui  Linli 《Theoretical and Applied Climatology》2017,129(1-2):385-396

Theoretical and Applied Climatology - The variation and trend in the frequency and duration of four types of high-impact weather (HIW) events were examined using daily surface climate data and...  相似文献