Prolonged Dry Episodes Over Northern Eurasia and North America: New Tendencies Emerging During the Last 40 Years
Abstract
A disproportionate increase in precipitation coming from intense rain events, in the situation of general warming (thus, an extension of the vegetation period with intensive transpiration) and an insignificant change in total precipitation could lead to an increase in the frequency of potentially serious type of extreme events: prolonged periods without precipitation (even when the mean seasonal rainfall totals increase). We investigated whether this development is already occurring during the past several decades over North America and Northern Eurasia, for the same period when changes in frequency of intense precipitation events are being observed. Lengthy strings of "dry" days without sizeable (>1.0mm) precipitation were assessed only during the warm season (defined as a period when mean daily temperature is above the 5°C threshold) when water is intensively used for transpiration and prolonged periods without sizable rainfall represent a hazard for terrestrial ecosystem's health and agriculture. For these strings we estimate the distribution of their frequency and duration and study their trends (if any) for dry regions within North America and the former USSR. During the past four decades, the mean duration of prolonged dry episodes (20-days or longer in southeastern Canada, 1-month or longer in the southern Siberia and Russian Far East, eastern United States, and along the Gulf Coast of Mexico and 2-months or longer in the Southwestern United States and Northern Mexico) has significantly increased. Over the Asian part of Russia we also observed an increase in duration of "fire" weather conditions. Research of the latest tendencies of prolonged dry episodes across the newly independent Central Asia States is hampered by data access problems.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- Bibcode:
- 2007AGUFMGC23A0974G
- Keywords:
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- 1637 Regional climate change;
- 1812 Drought;
- 1817 Extreme events;
- 1836 Hydrological cycles and budgets (1218;
- 1655);
- 1854 Precipitation (3354)