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Characteristics and Establishment of Objective Identification Standard and Perdictor of Foehn Winds in Urumqi on the North Slope of Middle Tianshan Mountains of China
Ayitikan, M.; Li, X.; He, Q.; Musha, Y.; Tang, H.; Li, S.; Zhong, Y.; Ren, G. Characteristics and Establishment of Objective Identification Criteria and Predictors for Foehn Winds in Urumqi, China. Atmosphere2023, 14, 1206.
Ayitikan, M.; Li, X.; He, Q.; Musha, Y.; Tang, H.; Li, S.; Zhong, Y.; Ren, G. Characteristics and Establishment of Objective Identification Criteria and Predictors for Foehn Winds in Urumqi, China. Atmosphere 2023, 14, 1206.
Ayitikan, M.; Li, X.; He, Q.; Musha, Y.; Tang, H.; Li, S.; Zhong, Y.; Ren, G. Characteristics and Establishment of Objective Identification Criteria and Predictors for Foehn Winds in Urumqi, China. Atmosphere2023, 14, 1206.
Ayitikan, M.; Li, X.; He, Q.; Musha, Y.; Tang, H.; Li, S.; Zhong, Y.; Ren, G. Characteristics and Establishment of Objective Identification Criteria and Predictors for Foehn Winds in Urumqi, China. Atmosphere 2023, 14, 1206.
Abstract
Due to the special terrain of Urumqi (in the valley area), which often triggers strong foehn weather, and causes huge losses to local people's lives and social economy. This study uses in-situ surface meteorological variables (including the hourly temperature, pressure, humidity, wind, etc.) from the Urumqi Meteorological Station (downstream station, DS) and the Dabancheng Meteorological Station (upstream station, US) in the Middle Tianshan Valley and NCEP/NCAR reanalysis data from 2008 to 2022. A dataset of the foehn weather process at DS in the past 15 years is established and the variation patterns of each meteorological variable during the process of foehn is analyzed. Based on the physical mechanism of the occurrence of foehn, a three-element identification standard for foehn in Urumqi is established by comparing and analyzing the variation of wind direction (WD), wind speed (WS), and the difference of potential temperature (Δθ) between DS and US during the period of foehn and non-foehn from 2013 to 2022, namely: 94°≤ 2-minute average WD ≤168°, 2-minute average WS ≥2.0 m/s, and Δθ between DS and US ≥ 0.29 K. According to the test and evaluation, the three-element identification standard has an accuracy of 82.96%, and a hit rate of 89.50% for the occurrence of foehn in Urumqi from 2008 to 2012. Moreover, the hit rate of foehn identification is 100% for strong wind or above (i.e., 2-minute average WS ≥10.8 m/s) WS. In addition, combined with two predictors of sea-level pressure difference (ΔP) and Δθ between DS and US, forecasting foehn can be more accurately predicted than a single forecasting factor. When ΔP ≤ -12 hPa and Δθ≥5 K, the probability of the occurrence of foehn is more than 90%. This study provides certain reference and application value for the weather forecasting operation of foehn.
Keywords
Foehn; Wind direction and speed; Potential temperature difference; Identification standard
Subject
Environmental and Earth Sciences, Atmospheric Science and Meteorology
Copyright:
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
