Arkstorm

A Arkstorm, correct ARkStorm for Atmospheric River kilo Storm ( engl. Atmospheric River 1000 storm ) is examined, the designation for a weather scenario, the United States Geological Survey, the heavy winter storms with heavy rainfall in California. The basis for the scenario similar rains that began on Christmas Eve 1861, and 45 days of continuous rain brought. Large parts of the Central Valley were impassable and Los Angeles became a muddy lake. The scenario was created to test the civil protection measures and is a link in a chain of such scenarios of possible natural disasters such as earthquakes, tsunamis, forest fires, landslides and coastal erosion.

In Arkstorm scenario, the measurement data of two as " Pineapple Express" were merged designated weather conditions in January 1969 and February 1986, simulated in modern computers. The calculated results were heavy rains for 23 days. So this scenario will not produce the worst possible expression, is therefore not a worst- case scenario. Studies of sediments of the river terraces of major rivers in California show that neither the scenario nor the rains of 1862, the worst in California history were. For California, the incidence of Arkstorms is estimated to an incident in 100 to 200 years.

Effects of the scenario

According to the scenario, the Central Valley would be flooded over a length of about 500 km and a width of 20 km. Also the populous centers of Los Angeles, San Francisco, San Diego and Orange County would be affected by severe flooding. The total cost of the hypothetical damage is estimated at over 700 billion U.S. dollars. Based on the scenario were doubts about the ability of public administration to cope with such a scenario aloud. There have been trade-offs, if significant amounts of money should be invested in disaster prevention measures or whether much larger sums in the treatment of the consequences of such a scenario should be invested.

The scenario has attracted significant media interest and is now being investigated in other regions of the world. Thus the meteorologist Andreas H. Fink of the University of Cologne called similar rainfall for Europe possible.

Meteorological data

Arkstorms caused by tropical air masses, which are shifted in stable atmospheric rivers over several days in coastal regions. The amount of water present in the streams is specified with the 7 to 15 times the Mississippi. On the west coasts of continents, it can gather, possibly favored by mountain chains come to orographic rainfall and rain heavily over several days. Reports from the winter 1861/62 speak of 45 days of rain and let the scenario so plausible. In addition, sediment samples were able to confirm the occurrence of similar incidents historically from the Central Valley.

The atmospheric fluxes were discovered only in 1998 by Yong Zhu and Reginald Newell from the Massachusetts Institute of Technology through the analysis of data of the European Centre for Medium-Range Weather Forecasts. Thus, atmospheric currents for the deflection of about 95 percent of the humidity in the direction of the poles are responsible. On the west coasts of continents this can lead to heavy rain, such as the fall of 2009 in the UK or Spain.