July 25, 2013. Recently, a study on heat waves, brought quite interesting results, showing that the amount and intensity of such events will increase in the north-western Pacific countries, not during the day and at night.
Experts from the University of Oregon and Washington have documented 15 instances of "night heat waves" in the period from 1901 to 2009. Ten of them came after 1990, 5 were from the short period from 2006 to 2009. While the study materials were prepared for the press, became aware of the occurrence thereof, even a heat wave at the end of June this year, which lasted until the first days of July. In this day of heat waves during the same period (1901-2009) was only 13. And only two of them were the last 20 years.
Presumable cause prolongation of heat waves on the dark is the nature of moisture in the air to global warming. At night, increasing humidity at low altitudes "locks" the heat inside the city, causing the effect of the heat wave. For cities north-west, located on the shores of the Pacific Ocean, hot nights are not normal.
Often the onset of daytime and nighttime heat waves coincide. That was in 2009, when the U.S. state of Washington was recorded new all-time record (+39 ° C), and in the cities of Oregon, a Portland, Corvallis and Medford, air warmed up to +40 ° C. Heatwave then lasted three days. Which coincided with the day the night the heat wave took a lot more time (8 days), appearing due to the consolidation of monsoon moisture over land that used to happen very rarely.