Abstract
Recent studies show mid-latitude western boundary currents (WBCs) substantially influence the atmosphere aloft, and an important feature is enhanced rain band over the WBCs in climatological mean field. However, how such long-term, climate phenomena are related to shorter, weather timescale phenomena are generally remained to be explored. In this paper, diurnal precipitation and cloud variations are investigated global mid-latitude oceans with emphasis on air–sea interactions over WBCs using satellite-derived precipitation and outgoing longwave radiation (OLR) datasets. Strong 24-h period components of precipitations are found over the Gulf Stream in summer and over the Kuroshio in the East China Sea in early summer (Baiu–Meiyu season), respectively. Similar diurnal precipitations are not observed in WBCs in the Southern Hemisphere year around. The diurnal precipitation cycles over the Gulf Stream and the Kuroshio exhibit peak phases in the early to late morning for the Gulf Stream and late morning to early afternoon for the Kuroshio, with southeastward phase propagations. High cloud frequency derived from OLR data exhibit consistent diurnal cycles. A substantial difference of diurnal cycles between the Gulf Stream and the Kuroshio regions are associated with the large-scale Baiu–Meiyu rain and cloud bands for the latter region. Diurnal precipitation and high cloud variability is found in the vicinity of the Kuroshio itself, embedded in the Baiu–Meiyu rain and cloud bands distributing in a wider area without a strong diurnal component. The spatial and seasonal distributions of the diurnal variability over these WBCs strongly suggests that the diurnal precipitation and cloud cycles are essential aspects of deep heating mode of atmospheric response recently reported for these WBCs. These results indicate that these WBCs in the Northern Hemisphere play an important role in modulating short-term precipitation variations, and on the other hand diurnal variability can be a substantial agent for the mid-latitude air–sea interaction.
Highlights
How mid-latitude oceans fronts, associated with western boundary currents (WBCs) and meso-scale eddies, influence the overlying atmosphere is a rapidly developing research field
Takebayashi Department of Natural History Sciences, Graduate School of Science, Hokkaido University, Room 319, Rigaku Building No 8, N10, W8, Kita‐ku, 060‐0810 Sapporo, Japan e-mail: minobe@sci.hokudai.ac.jp and seasonal distributions of the diurnal variability over these WBCs strongly suggests that the diurnal precipitation and cloud cycles are essential aspects of deep heating mode of atmospheric response recently reported for these WBCs. These results indicate that these WBCs in the Northern Hemisphere play an important role in modulating shortterm precipitation variations, and on the other hand diurnal variability can be a substantial agent for the mid-latitude air–sea interaction
In order to know whether the major features found in the outgoing longwave radiation (OLR)-based high cloud frequency are consistent with independent cloud data, we examine cloud amount for high-level clouds of D2 dataset of International Satellite Cloud Climatology Project (ISCCP) for a period from 2000 to 2009 (Rossow and Schiffer 1999)
Summary
How mid-latitude oceans fronts, associated with western boundary currents (WBCs) and meso-scale eddies, influence the overlying atmosphere is a rapidly developing research field. A deep heating mode as energetic as that over the Gulf Stream is found in the atmospheric response over the Kuroshio in the East China Sea in June, i.e., middle of early summer rain season in this region (Sasaki et al 2012). This long-lasting precipitation phenomenon prevailing from southeast China to Japan is called Baiu in Japan and Meiyu in China. This global analysis reveals strong diurnal precipitation variability in summer over the Gulf Stream and over the Kuroshio in the East China Sea. in the following two sections
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
