Diurnal precipitation variability over the Gulf Stream and the
Kuroshio Shoshiro Minobe and Shogo Takabeyashi (Hokkaido
University, Sapporo, Japan) Outline Introduction Global View Gulf
Stream region Kuroshio region Summary, schematics &
discussion
Slide 2
Introduction 1/3 A challenge of air-sea interaction studies is
to understand how high-frequency variability (weather) interact
with low-frequency phenomena (climate). A number of studies are
conducted for synoptic disturbances. Today, I would like to show
that another interesting high-frequency phenomenon, diurnal
variability, plays important role in air-sea interaction over WBCs
as implicitly mentioned by Minobe et al. (2008). 1
Slide 3
Introduction 2/3 They showed 2 Minobe et al. (2008 Nature)
Occurrence frequency of daytime satellite- derived OLR levels lower
than 160 W m -2 (colour). This implies that the Gulf Stream
influence is not clear in nighttime. So, diurnal variability should
occur.
Slide 4
Introduction 3/3 3 Kikuchi and Wang (2007) Actually, diurnal
variability of precipitations are seen in previous studies, but
they focus their attentions on tropics and did not mention about
mid-latitude air-sea interaction nor WBCs. So, we explorer how
diurnal cycles are related to WBCs.
Slide 5
Data Satellite precipitation products GSMaP MVK v. 5 as the
main precipitation data 0.1x0.1, hourly, March 2000 to December
2010 Microwave + IR satellite (movement vector & brightness)
with Kalman filter TRMM 3B42 v7 for check 0.25x0.25, 3 hourly,
analysis period is 2000-2010 Microwave (at available points) + IR
(otherwise) temporal & spatial heterogeneity OLR for high
clouds NASA/GEWEX Surface Radiation Budget (SRB) project ver. 3.1,
1x1, 3 hourly analysis period is 2000-2007 (data end at 2007 Dec.)
Occurrence rate of OLR
Slide 6
Methods Harmonic analysis of diurnal climatology in each month
and each season. 5 We also define relative amplitude (RA) RA
amp/mean For a sinusoidal diurnal climatology, 0
