TAO buoy temp. + ASCAT

Moment of truth: composite ASCAT winds against buoy temperature; start with western equatorial Pacific. We define CPs by a temperature drop of 1.5°C over 1h, or 2°C over 2 h. After ASCAT winds, repeat compositing procedure for OLR, and for Seawinds (winds + rr).

Now at 6°N.

Seasonal cycle of CPs looks different at two buoys only 550 km apart. 0N appears to peak in DJF, while 5N hits a minimum in DJF (?). Who knows, maybe this metric is sensitive to the CP definition, or maybe need a few more years for reliable estimate.

Buoys used to form composite.

CP count in each bin, i.e. number of CPs for which ASCAT data is available. n≈100 at nadir (near t=0). Red line should be close to double blue line. ±12 h bins larger (blue line) since they actually extend to ±13 h.

Composite buoy air temperature (left) shows that air temperature doesn’t fully recover, even by 12 h. Min(div) and max(div), at right, show nothing. Simplest explanation is that satellite can’t resolve downdrafts. Other explanations include a mismatch in the buoy clock (check against OLR), sensitivity to low winds (filter for stronger winds), or rain contamination (filter for clear-sky CPs).

Composite winds and divergence show very little in common with NICAM. Easterly background winds still evident. Contour levels are 0.5×10 -5 s -1. Discouraging that no signal exists at 0, 1 hr.

Comparison of buoy wind speed vs. “point” ASCAT wind speed. Buoys show nice bump at t=-1,0, consistent with Addis et al., Young et al Maybe search for highest wind speed in box? ASCAT might be able to resolve small-scale wake at buoy, but perhaps somewhere in box shows higher wind speed.

Now compare (vector- averaged) u,v. Buoy and ASCAT show hint of W-IGW propagation, but phase is different. ASCAT, especially, appears to show a prominent wave with period 12–13 h. ASCAT u signal is actually consistent with divergence as W-IGW passes location. I should extend bins to ±24 h to hopefully better resolve wave. Also add 2 h spacing. Also I should record actual (u,v) values so I can compute std(u), std(v) in each bin.

Top: min(IR temp.) within 115km of buoy, for Nov 2012-Jan Standard error shown by dashed lines. Right: Composite maps of IR temperature centered at buoy, for Nov 2012-Jan Lowest contour at t=1h is for 239K, ΔT≈25K. This is significant (cf. top plot), but also suggests that some shallow convection contributes, since “deep” usually 210K. Note that the spatial scale of the temperature depression is ~200 km.

Composite buoy wind speed for just 3 months, now plotted with standard error (dashed). CP “spike” in wind speed easily exceeds standard error, even for this short record.

Now at 6°N.