• Main Authors: Mototaka Nakamura, Takeshi Enomoto, Shozo Yamane
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2004
• Subjects: heatwave; Europe; blocking; eddy forcing; North Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.522.3435; http://www.jamstec.go.jp/esc/publication/journal/jes_vol.2/pdf/JES2_nakamura.pdf

Abstract A devastating heatwave that struck much of western Europe during the first two weeks of August, 2003 was studied as a case of strong summer blocking, using high-resolution global atmospheric simulation model output and the NCEP/NCAR reanalyses. From the reanalyses data diagnoses, the heatwave was found to be caused by an eastward shift in the location of a summer blocking that occurs sometimes over the North Atlantic. Further diagnoses reveal a region of anomalously strong vertical flux of high-frequency waves in the central North Atlantic preceding the heatwave, suggesting that it may be a potential cause of the eastward shift. Six simulations of a period, July 1 – August 15 2003, were performed with AFES, using the daily observed SST in the control run and the climatological SST in parts or all of oceans in the other runs. The control run reproduced the heatwave reasonably well, as well as some of the wave forcing found in the reanalyses data. In three other runs that were forced with the climatological SST everywhere or in selected regions did not reproduce the heatwave at all, with a blocking occurring farther west of that in the control run. These runs did not produce the suspected key wave forcing for the heatwave either. The results suggest an important role of the anomalously strong wave forcing in the central North Atlantic in shifting the blocking location and, thus, bringing the heatwave to western Europe.