Anomalous circulation patterns associated with 2011 heavy rainfall over northern Tanzania

2021 ◽  
Author(s):  
Laban Lameck Kebacho
Keyword(s):  
Heavy Rainfall ◽  
Northern Tanzania ◽  
Circulation Patterns ◽  
Anomalous Circulation

scholarly journals A Comparison of Three Prolonged Periods of Heavy Rainfall over the Hawaiian Islands

2012 ◽  
Vol 51 (4) ◽  
pp. 722-744 ◽  
Author(s):  
I. M. Shiromani Jayawardena ◽  
Yi-Leng Chen ◽  
Andrew J. Nash ◽  
Kevin Kodama
Keyword(s):  
Heavy Rainfall ◽  
Large Scale ◽  
Hawaiian Islands ◽  
Hadley Circulation ◽  
Wind Component ◽  
Central Pacific ◽  
Optimal Position ◽  
Subtropical Jet ◽  
Circulation Patterns ◽  
Stormy Weather

AbstractThe anomalous circulation patterns during an unusually prolonged stormy-weather period in Hawaii from 19 February to 2 April 2006 are analyzed and are compared with those of two previously known prolonged heavy-rainfall periods (March 1951 and February 1979). The circulation patterns for these three periods are characterized by 1) a negative Pacific–North American (PNA) pattern in the midlatitudes with a blocking high southwest of the Aleutian Islands, 2) retraction and splitting of the zonal jet into a polar jet north of 50°N and a persistent subtropical jet to the south over the central Pacific Ocean, 3) an anomalous low west of the Hawaiian Islands embedded in the subtropical jet, and 4) a weaker-than-normal Hadley circulation in the mid-Pacific. The moisture advected from low latitudes by the southerly wind component east of the persistent anomalous low, combined with upward motion, provides the large-scale setting for the unusually prolonged unsettled weather across the Hawaiian Islands. For all three cases, the prolonged stormy weather started after the onset of large-scale blocking and a negative PNA pattern over the North Pacific and the occurrence of a persistent anomalous low embedded in the subtropical jet west of the Hawaiian Islands. Furthermore, the persistent low was located at the optimal position to bring moisture from the central equatorial Pacific to Hawaii. The stormy weather ceased after the midlatitude blocking pattern weakened and the anomalous low in the subtropics decayed and/or shifted westward. There are no apparent common precursors in the 2-week period prior to the prolonged stormy weather among these three cases, however.

Weather circulation patterns as precursor of heavy rainfall events: an application to Sicily, Italy

2020 ◽  
Author(s):  
Giuseppe Cipolla ◽  
Antonio Francipane ◽  
Leonardo Noto
Keyword(s):  
Climate Change ◽  
Atmospheric Circulation ◽  
Heavy Rainfall ◽  
Winter Season ◽  
Flash Floods ◽  
Convective Precipitation ◽  
Rainfall Events ◽  
Circulation Patterns ◽  
Heavy Rainfall Events ◽  
Economic Damages

<p>Since the impacts of climate change on the environment have been constantly rising over the last decades, scientists have paid much attention to understanding the effects of this phenomenon. Climate change leads to different kinds of extremes, such as heavy rainfall events, characterized by short duration and high intensity, and drought, which can cause the problem of water scarcity over a certain area. These types of extreme events cause several damages for the affected areas since they can result in loss of human lives and economic damages. In particular, heavy rainfall events, which are often associated with convective precipitation because of their characteristics, may result in flash floods, especially when they hit small catchments with low times of concentration, thus causing economic damages and, more relevantly, human lives losses.</p><p>The increasing occurrence of heavy rainfall events in many areas of Europe, also in Italy, over the last few years, has contributed to raising the importance of understanding which factors could be recognized as drivers of these events. In this perspective, it is possible to identify in atmospheric circulation one of the causes of severe rainfall events occurrence since some air fluxes, generated from certain schemes of atmospheric circulation, could lead to the accumulation of moisture within a certain volume of the atmosphere, hence to the occurrence of rainfall.</p><p>Since even the Sicily (Italy) has been experimenting heavy rainfall events and consequent flash floods and urban floods in the last years, this work aims to find out a relationship between some weather circulation patterns, developed by the UK Met Office, and the rainfall Annual MAXima (AMAX) for the Sicily, recorded by the rain gauge network of Autorità di Bacino - Regione Siciliana. The possible connection between AMAX and WPs has been investigated in order to define some specific schemes of atmospheric circulation that are responsible for leading to the occurrence of AMAX in Sicily. In order to do this, a database containing the AMAX of all the available gauges for the Sicily has been used. A distinction between AMAX occurred in summer and winter season and their related WPs has been performed as well, with the goal to understand the possible influence of WPs on the summer and winter AMAX. Furthermore, in order to distinguish convective from stratiform AMAX, some analyses on reanalysis data, namely the CAPE and the Vertical Integral of Divergence of Moisture Flux (VIDMF), have been done.</p>

scholarly journals Seasonal probability forecasts of december-january-february precipitation in northern Uruguay and Rio Grande do Sul obtained with the coupled forecast system v2 of NOAA and statistical downscaling

2012 ◽  
Vol 27 (4) ◽  
pp. 377-387 ◽  
Author(s):  
Gabriel Cazes Boezio ◽  
Stefanie Talento ◽  
Gabriel Jorge Pisciottano Jalabert
Keyword(s):  
South America ◽  
Numerical Models ◽  
Austral Summer ◽  
Rio Grande ◽  
Meridional Wind ◽  
Rio Grande Do Sul ◽  
Forecast System ◽  
Seasonal Predictability ◽  
Circulation Patterns ◽  
Anomalous Circulation

The present work analyses the inter-seasonal predictability of precipitation during the austral summer in a subregion of Southeastern South America that includes Rio Grande do Sul and Northern Uruguay (RGS-NU), and proposes a methodology to produce probabilistic precipitation forecasts for this region, based on the use of NOAA CFS v2. It is found that the correlation between ENSO and the precipitation over RGS-NU during December-January-February is statistically significant after the late 70's, but not before. Considering that this relationship changes in different multidecadal periods, it is useful to explore a forecast system based on numerical models. We studied the hindcasts from NOAA CFS v2 initialized during October of the years 1983 to 2009, and found that the hindcasts of meridional wind at 850 hPa averaged over certain region of South America have statistically significant skill, in terms of correlation, to predict the observed precipitation over RGS-NU. The proposed forecasts are based on this relationship. The CFS v2 hindcasts also show realistic anomalous circulation patterns associated with the anomalous precipitation in the region and the season considered. This suggests that the forecasts may be further improved by using regional models combined with the CFS v2 outputs.

scholarly journals Simulation of daily variation of precipitation during anomalously-wet dry season event over the western Maritime Continent

2021 ◽  
Vol 893 (1) ◽  
pp. 012046
Author(s):  
E Yulihastin ◽  
Suaydhi ◽  
H Satyawardhana ◽  
C N Ihsan
Keyword(s):  
Climate Model ◽  
Regional Climate ◽  
Tropical Rainfall Measuring Mission ◽  
Satellite Observation ◽  
Atmospheric Model ◽  
Dry Season ◽  
Maritime Continent ◽  
Local Circulation ◽  
Circulation Patterns ◽  
Anomalous Circulation

Abstract Local seas play a significant role in causing anomalously wet of the dry season over the Indonesia Maritime Continent (10°S-8°N, 95-145°E). As a result, modeling the anomalously-wet dry season over Indonesia lead challenges due to several subregional processes over local seas could not be captured well in the regional climate model. This study explores subregions processes of sea-air interaction over the western Maritime Continent by simulating diurnal precipitation using Cubic Conformal Atmospheric Model (CCAM) with a spatial resolution of 32 km during the anomalously-wet dry season periods during May-to-September (MJJAS) 2020. The simulated results were confirmed by precipitation data from Tropical Rainfall Measuring Mission (TRMM) satellite observation. The results show anomalous circulation patterns induce anomalous regional precipitation over western MC is induced by anomalous circulation patterns over four keys of seas subregion, i.e., Indian Ocean, South China Sea, southern Sumatra (Lampung and Sunda strait), and the Java Sea. Furthermore, the anomalous circulation also modulates anomalous local circulation and enhances surface water vapor by an increased surface latent heat flux.

scholarly journals Upper troposphere circulation anomalies over Asia-Pacific region associated with the interannual variation of Indian summer monsoon

MAUSAM ◽  
2021 ◽  
Vol 49 (4) ◽  
pp. 461-468
Author(s):  
D. S. PAI ◽  
M. RAJEEVAN ◽  
U. S. DE
Keyword(s):  
Monsoon Season ◽  
Cyclonic Circulation ◽  
Asia Pacific ◽  
Asia Pacific Region ◽  
Circulation Anomaly ◽  
Upper Troposphere ◽  
Circulation Patterns ◽  
Anomalous Circulation ◽  
Mean Vector ◽  
Vector Wind

Monthly mean vector wind and geopotential heights at 200 hPa of 67 radiosonde stations from Asia Pacific regions for the period 1963-1988 are used to examine the composite circulation anomaly patterns for the month of May and the monsoon season (June- September) with respect to good monsoon years and bad monsoon years (both associated with ENSO and not associated with ENSO). There are significant differences in the anomalous circulation features between good and bad monsoon years. During the month of May an anomalous anticyclonic (cyclonic) circulation over-central Asia and an anomalous cyclonic (anticyclonic) circulation over Pacific ocean were observed during good (bad) monsoon years. These anomalies persist in the subsequent monsoon season. The key mechanisms of the development of these anomalous circulation  patterns and their consequences are discussed.

scholarly journals Multiscale Causes of Persistent Heavy Rainfall in the Meiyu Period over the Middle and Lower Reaches of the Yangtze River

2021 ◽  
Vol 9 ◽  
Author(s):  
Yicong Xia ◽  
Qian Huang ◽  
Suxiang Yao ◽  
Tianle Sun
Keyword(s):  
Water Vapor ◽  
Yangtze River ◽  
Heavy Rainfall ◽  
Observation Data ◽  
The Yangtze River ◽  
Synoptic Scale ◽  
Circulation Patterns ◽  
Persistent Heavy Rainfall ◽  
The Difference ◽  
Heavy Rainfall Events

Based on observation data supplied by the Chinese Meteorological Administration (CMA) and reanalysis datasets provided by the ECMWF, the multiscale causes of persistent heavy rainfall events (PHREs) that occurred from 1979 to 2018 during Meiyu periods over the middle and lower reaches of the Yangtze River (MLYR) are investigated. During Meiyu periods, precipitation shows obvious interannual variabilities. In PHRE years, the contribution rate of persistent heavy rainfall to the total precipitation is approximately 57%. Precipitation also shows significant synoptic-scale (less than 10 days) characteristics. Through the quantitative diagnosis of interactions among background-scale (greater than 30 days), quasi-biweekly-scale (10–30-days), and synoptic-scale variables, the possible causes of PHREs are explored. The results reveal that the difference in precipitation intensity between PHRE years and non-PHRE years is determined by the background water vapor, background wind and synoptic-scale wind conditions. In PHRE years, the prevailing background southwesterly winds from lower latitudes provide more background water vapor, and more mean kinetic energy is converted to perturbation energy. Moreover, the active synoptic-scale oscillations from higher latitudes and the convergence of Rossby wave disturbance energy over the MLYR could also cause the occurrence and maintenance of PHREs during Meiyu periods. The multiscale causes and corresponding circulation patterns in 2020 PHREs are similar to PHREs years.

Low Latitude Vorticity Injections and the Development of Large Scale Anomalous Circulation Patterns

1956 ◽  
Vol 37 (6) ◽  
pp. 270-275 ◽  
Author(s):  
Robert D. Elliott
Keyword(s):  
Large Scale ◽  
Middle Latitude ◽  
Vorticity Field ◽  
Low Latitude ◽  
Circulation Patterns ◽  
Low Latitudes ◽  
Anomalous Circulation ◽  
Composite Maps

Some general characteristics of synoptic developments in the 500 mb vorticity field are discussed with particular attention devoted to sudden injections of vorticity and to changes in circulation patterns downwind therefrom. Attention is then focused on vorticity injections generated at low latitudes, but not too low to interact in an important way with the middle latitude circulation. Composite maps based upon numerous cases are shown which reveal the development of large scale anomalous patterns in the westerlies during the 3 days subsequent to low latitude vorticity injection. The forecasting implications are discussed.

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