Search results for "tropics"

Orographic Effects and Evaporative Cooling along a Subtropical Cold Front: The Case of the Spectacular Saharan Dust Outbreak of March 2004

2012

Abstract On 2 March 2004 a marked upper-level trough and an associated surface cold front penetrated into the Sahara. High winds along and behind this frontal system led to an extraordinary, large-scale, and long-lived dust outbreak, accompanied by significant precipitation over parts of Algeria, Tunisia, and Libya. This paper uses sensitivity simulations with the limited-area model developed by the Consortium for Small-Scale Modeling (COSMO) together with analysis data and surface observations to test several hypotheses on the dynamics of this case proposed in previous work. It is demonstrated that air over central Algeria is cooled by evaporation of frontal precipitation, substantially en…

Dynamics of a local Alpine flooding event in October 2011: moisture source and large‐scale circulation

2014

Alpine heavy precipitation events often affect small catchments, although the circulation pattern leading to the event extends over the entire North Atlantic. The various scale interactions involved are particularly challenging for the numerical weather prediction of such events. Unlike previous studies focusing on the southern Alps, here a comprehensive study of a heavy precipitation event in the northern Alps in October 2011 is presented with particular focus on the role of the large-scale circulation in the North Atlantic/European region. During the event exceptionally high amounts of total precipitable water occurred in and north of the Alps. This moisture was initially transported alon…

On the structural changes in the Brewer-Dobson circulation after 2000

2010

In this paper we present evidence that the observed increase in tropical upwelling after the year 2000 may be attributed to a change in the Brewer-Dobson circulation pattern. For this purpose, we use the concept of transit times derived from residual circulation trajectories and different in-situ measurements of ozone and nitrous dioxide. Observations from the Canadian midlatitude ozone profile record, probability density functions of in-situ N<sub>2</sub>O observations and a shift of the N<sub>2</sub>O-O<sub>3</sub> correlation slopes, taken together, indicate that the increased upwelling in the tropics after the year 2000 appears to have triggered an in…

20th century droughts in southern Africa: spatial and temporal variability, teleconnections with oceanic and atmospheric conditions

2001

Southern African rainfall does not show any trend to desiccation during the 20th century. However, the subcontinent experienced particularly severe droughts in the 1980s and at the beginning of the 1990s and the magnitude of the interannual summer rainfall variability shows significant changes. Modifications of the intensity and spatial extension of droughts is associated with changes in ocean–atmosphere teleconnection patterns. This paper focuses mostly on the well-documented 1950–1988 period and on late summer season (January–March). A principal component analysis on southern African rainfall highlights modifications of the rainfall variability magnitude. The 1970–1988 period had more var…

Modification of the southern African rainfall variability/ENSO relationship since the late 1960s

2000

Analysis of 149 raingauge series (1946–1988) shows a weak positive correlation between late summer rainfalls (January–March) in tropical southern Africa and the Southern Oscillation Index (SOI). The correlation coefficients have been unstable since World War II. They were close to zero before 1970 and significant thereafter. Before 1970, southern African late summer rainfalls were more specifically correlated with regional patterns of sea surface temperature (SST), mainly over the southwestern Indian Ocean. After 1970, teleconnections with near global SST anomaly patterns, i.e. over the central Pacific and Indian oceans, dominate the regional connections. The increase in the sensitivity of …

The economic impact of future increase in tropical cyclones in Japan

2009

Published version of an article from the journal:Natural Hazards. Also available from SpringerLink: http://dx.doi.org/10.1007/s11069-010-9522-9 This article estimates the non-first-order economic loss in Japan due to a future increase in tropical cyclones. One possible effect of global warming could be the increase in intensity of tropical cyclones. Using historical storm tracks between the years 1978 and 2007 and altering their intensities due to this potential increase in their intensity, this paper calculates the future potential regional GDP loss in a certain area that is affected by tropical cyclones. Most of the literature is concerned with physical damage and the loss of lives due to…

Dynamics of tropical–extratropical interactions and extreme precipitation events in Saudi Arabia in autumn, winter and spring

2016

Sea-surface temperature co-variability in the Southern Atlantic and Indian Oceans and its connections with the atmospheric circulation in the Souther…

2003

The relationship between sea-surface temperature (SST) inter-annual variability at the subtropical and midlatitudes of the southern Atlantic and Indian Oceans and its links with the atmospheric circulation in the Southern Hemisphere are investigated over the 1950–1999 period. Exploratory analysis using singular value decomposition and further investigations based on simple indices show that a large part of regional SST variability is common between the southwestern parts of both basins at subtropical and midlatitudes during the austral summer. Interestingly, these areas are also significantly associated with the far southwestern Pacific (Tasman Sea area). The patterns and time series of co-…

Monthly survival of African Sylvia warblers in a seasonally arid tropical environment

2006

Latitudinal gradients of life-history traits in animals are thought to be shaped by environmental variables. For example, it has been suggested that the increase in avian clutch size from the tropics towards the northern temperate regions is caused by a reduced survival of adult birds in the north due to increasing environmental seasonality. However, the tropical savannahs of East Africa show pronounced seasonality in resources caused by distinct rainy and dry seasons. This raises the question of whether survival and other life-history traits of birds living in these tropical savannahs are influenced by this seasonality, making them more similar to northern temperate species. We used 2-year…

Life-history of two African Sylvia warblers: low annual fecundity and long post-fledging care

2004

The investigation of factors that cause differences in life-history traits between temperate and tropical birds is often hampered by a lack of knowledge about tropical species. Even within the well-known warblers of the genus Sylvia, which include resident species from temperate and tropical regions as well as migrants, there are few data from tropical species. We investigated the breeding biology of the tropical species Sylvia lugens and S. boehmi in a 2-year study in Kenya. Both species had a clutch size of 2.0 and laid c. 3.7 clutches per year. Breeding was characterized by long incubation periods (S. lugens 14.5 days, S. boehmi 15.0 days), long nestling periods (16.0 and 12.9 days, resp…