Abstract
Abstract. The purpose of this study is to understand atmospheric factors, which cause mudflow variability on interannual and longer timescales, from local to synoptic scales. In a first step, historical data of mudflow occurrences in Uzbekistan provided by the Centre of Hydrometeorological Service of the Republic of Uzbekistan (Uzhydromet) for more than 140 years were analysed. During the investigation period a total of about 3000 mudflow events were observed with about 21 events per year on average. The majority of mudflows occur during the advection of westerly airflow when moist air from central and southern Europe reaches Uzbekistan. This synoptic weather type (SWT) can be related to one of the 15 primary synoptic circulation types over central Asia (CA) and Uzbekistan, which were subjectively derived by Bugayev and Giorgio in the 1930s and 1940s. To understand the main atmospheric regimes steering the variability in mudflow occurrences, we additionally applied an objective classification following the circulation weather type (CWT) approach. By means of the CWT approach, we found that on mudflow days the frequencies of cyclonic (C), westerly (W), south-westerly (SW) and north-westerly (NW) stream flows are increased in comparison to the climatological frequency of the occurrence of these circulation weather patterns. Results confirm that CWT westerly airflow initiates relatively more mudflow events comparing to other CWTs in the study area. An integrated approach of the CWT classification and an antecedent daily rainfall model are combined together in logistic regression analysis to construct a mudflow-triggering precipitation threshold for every CWT class. In general W, SW and C weather types require less antecedent rainfall to trigger mudflow occurrences in the study area. This technique is thus shown to be applicable to coarse-resolution climate model diagnostics.
Highlights
Mudflows are amongst the most damaging and deadly natural hazards in Uzbekistan
The goals of this paper are a. to assess the link between the potential effects of synoptic conditions and the occurrence of extreme hydrometeorological mudflow episodes in Uzbekistan; b. to establish an objective method for airflow classification of synoptic conditions that will be applicable to a large set of atmosphere–ocean general circulation model (AOGCM) and regional climate model (RCM) members to investigate key factors of climate change impact on precipitation over Uzbekistan and central Asia (CA); c. to compare and validate this with pre-existing subjective classification approaches; Nat
We introduce a subjective method to classify synoptic conditions of CA and Uzbekistan as well as an objective approach known as circulation weather types (CWTs) to identify the major weather types leading to the formation of mudflows in the study area in Sect
Summary
Mudflows are amongst the most damaging and deadly natural hazards in Uzbekistan. Hungr et al (2014) suggest the term mudflow as a very rapid, sometimes extremely rapid, surging flow of saturated plastic soil in a steep channel involving significantly greater water content relative to the source material. In the river basins of Uzbekistan, mudflows generally occur during periods of intense rainfall or rapid snowmelt. The destructive power of a mudflow can be greatly increased moving downhill due to the accumulation of water and rocky mud. It can destroy riverbeds and banks of rivers, floodplains and even low terraces above the floodplain and other objects in its path (Chub et al, 2007)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
