Heavy rain is a kind of severe weather, often causing floods and serious soil erosion, leading to engineering losses, embankment rupture and crop flooding and other significant economic losses. Especially for some low-lying terrain areas, rainwater cannot quickly vent caused by farm water and soil moisture being too saturated, so it will cause more geological disasters. This article combines live and forecast data, aiming at the results of the mid-rainstorm forecast in North China during the period of 7.19-2016, and compares with the actual situation of rainstorm. We carry out the mid-term forecast of the rainstorm. The atmosphere is a kind of medium with various fluctuation phenomena, and its physical properties and changes are studied by the analysis of volatility which is an important research method. It is important to improve the accuracy of such severe weather forecasting rainstorms and to take precautionary measures in a timely manner to minimize the losses caused by rainstorms.
During July 19 to 20, 2016, the rainfall processed in most areas of the North China, mostly in Hebei Province, which caused floods in some parts of the province. And this caused multiple landslides and debris flow disasters. This has led some people to be besieged, and the death and disappearance of personnel.
According to incomplete statistics, as of 08:00 08, the province’s 11 prefectures and Dingzhou City, Xinji City, a total of 142.86 million people affected by the disaster. 35 people died due to disaster, missing 77 people, collapsed housing 27,890, damaged housing 83,108, crop affected area of 536 thousand hectares, harvest area of 17 thousand hectares. The direct economic losses caused by the disaster have reached 8.642 billion yuan. Up to now, all over the emergency resettlement resettled 211,642 people.
Therefore, it is of great significance to strengthen the study of medium-term forecasting of catastrophic weather events such as heavy rain, to prevent the devastating weather, to reduce the damage caused by the disaster and to protect the life and property of the masses.
Numerical weather prediction is based on the actual situation of the atmosphere, at a certain initial value and boundary conditions, through a large computer for numerical calculation, describing the evolution of the process of hydrodynamics and thermodynamic equations [
However, since the atmosphere is a continuous medium with a continuous motion scale spectrum, there is always some movement that is close to or less than the scale of the grid, regardless of the resolution of the pattern (see the commonly used numerical method for numerical weather forecasting) [
The live data used in this study were obtained from the Central Meteorological Observatory and the forecast data were obtained from the ECMWF (European Center for Medium-Range Weather Forecast [
The atmosphere is a kind of medium with various fluctuation phenomena, using the analysis of volatility to study its physical properties and changes in the law is an important research method. The flow of daily atmospheric movement type and meteorological elements of the change is always showing some fluctuations features that it shows are different scales of disturbance to the weather common influence. In order to gain insight into the various scales of interference moving in the circulation of the atmosphere and some of the weather use, to enhance our understanding of the physical mechanism of the weather process, often need to carry out spectral decomposition, the atmospheric movement in the scale into divide the different waves. In order to examine the rows of a single wave, we compare their role in circulation adjustment and the weather. The process of the contribution to expose its evolution and its weather. There is a physical connection.
EC precipitation monthly forecast reported at July 14 can see the northeast- southwest to the rain belt situation. For Jianghan, Huanghuai area rain belt, we give a better forecast, but the rainfall is too small.
Due to the complex climate in the context of El Niño, the Yellow River cyclone developed northward abnormally. EC model has a large deviation in forecasting cyclone development, and the precipitation intensity forecast in north China is weak and the extreme degree of precipitation is poor.
The forecast from July 18 gave a strong forecast of the rain belt in North China, but the precipitation intensity forecast is still weaker than the actual situation. At the same time, Jianghan region forecast rainfall is also weak. The results are shown in
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(b)
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EC month forecast 3 to 4 weeks before the forecast for this precipitation are without any forecasting skills. 2 weeks ago forecast heavy rainfall belt is located in the Yangtze River, than the live south.
The forecast of “+” “−” “+” type prediction jumps in the forecast of precipitation in North China from different reporting times. See
EC Monthly forecast 3 to 4 weeks before the forecast for 10% extreme precipitation without any indication. 2 weeks ago (July 11 reported that) extreme precipitation occurred in Jianghan, Huanghuai area. July 14 forecast precipitation in North China is lower than normal, to July 18 forecast to give extreme precipitation in North China. See
EC Monthly forecast 3 to 4 weeks before the forecast for 10% extreme precipitation are without any indication. 2 weeks ago (July 11 reported that) extreme precipitation occurred in Jianghan, Huanghuai area. The forecast for July 14 has reduced the probability and area of heavy precipitation. To the July 18 forecast to give extreme precipitation in North China. See
EC month forecast 3 to 4 weeks before the forecast think that the eastern part of China’s 850 hPa for the southwest airflow. 2 weeks ago in Jianghan, Huanghuai area forecast a shear line. To the July 18 forecast in the northern part of North China to see a low vortex appears.
This should also be a reason of EC month forecast 2 - 4 weeks forecast rain belt position, rainfall deviation. Contrast is shown in
The 500 hPa subtropical high ridge line is located at 24˚N. 588 line west to 108˚E. In the high latitude degree, there is a high-altitude tank near the Lake Baikal.
EC month forecast 3 to 4 weeks before the forecast that the subtropical high ridge line at 30˚N, which is north than the real situation. In the high latitude is the zonal airflow. To 1 to 2 weeks forecast to gradually close to the real situation. Contrast is shown in
Live 200 hPa South Asia high-pressure ridge eastward extension to the eastern part of China’s Huanghuai between.
The monthly forecast of the 200 hPa South Asia high-pressure ridge is located between the Yangtze River Basin and the JAC. Contrast is shown in
In this paper, the mid-term forecast transition of heavy rainstorm in North China from 19 to 20 July 2016 was analyzed by using conventional meteorological observation data and EC set forecast data. We get the following main conclusions:
1) The EC collection forecast shows a significant change in the forecast of the position and intensity of the rain belt around July 16th. It started 5d ahead of a better forecasting ability. The transition of the belt position and intensity is caused by the impact of the system forecast. EC set forecast from the beginning
of the newspaper reported on the 15th reported, near the 500 hPa low trough by the downstream to strengthen the high pressure ridge block, slowly eastward development. So it formed an “East high west low” stability situation. While the lower-level southwest vortex and southwest jet forecast position is northerly stronger intensity.
2) The height difference of the 500 hPa latitude potential of the ensemble forecast is obvious from 8d in advance. “East high west low” type relative rainfall forecast has better predictability. The change trend can provide reference for the medium-term forecast of heavy rainfall in North China.
Medium-term forecast in Europe and the United States have achieved some success. Especially the European Center’s forecast is more recognized. But because of the weather process and weather phenomena affected by many factors, with a certain degree of randomness, it is soon found that with the extension of forecasting time, the accuracy of the forecast is declining rapidly, which makes the mid-term weather forecast very difficult. Therefore, to improve the accuracy of the medium-term forecast is still an important part of future research.
This work was supported by the National Meteorological Center Youth Fund (Q201603 and Q201703), China.
Zhang, X.K., Liu, Q.Q. and Zhang, M.Y. (2017) The Mid- Term Model Forecast Test of North China Rainstorm from July 19th to 20th, 2016. Journal of Geoscience and Environment Protection, 5, 166-180. https://doi.org/10.4236/gep.2017.58014