questioning the importance of the cloud lifetime effect: the relative roles … · 2019-08-21 ·...
TRANSCRIPT
![Page 1: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/1.jpg)
Questioning the importance of the cloud lifetime effect: The relative
roles of drizzle and the sun Sandra Yuter
Matthew Miller, Casey Burleyson, Margaret Frey, Andrew Hall, Matthew Wilbanks, Simon deSzoeke+
and David Mechem* North Carolina State University
*University of Kansas +Oregon State University
10 March 2014
DOE ASR Science Team Meeting
![Page 2: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/2.jpg)
In this figure, a single cloud represents the average response of a field of clouds [Stevens and Feingold (2009) following Albrecht (1989)]
Remote ocean marine stratocumulus
![Page 3: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/3.jpg)
Diurnal cycle of Cloud Fraction (3° x 3° boxes)
![Page 4: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/4.jpg)
Potential Roles of Precipitation in Marine Stratocumulus Cloud Cover Changes
• Strong precipitation has been implicated in regional cloud cover change – Depletion of cloud liquid water – Reduced moisture transport between ocean surface and
cloud • Drizzle evaporates below cloud creating stable layer • Stable layer decouples the sub-cloud layer from
surface and inhibits moisture transport from surface into the cloud layer
– Oscillating behavior of open cellular clouds related to creation and convergence of cold pools (Feingold/Terai)
Also occurs during day
![Page 5: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/5.jpg)
Neglect of Common Cause?
![Page 6: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/6.jpg)
Stevens et al. 2005 example from DYCOMS II
~5-10km
~1.5 km
6
730am local time (after sunrise)
![Page 7: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/7.jpg)
Precipitation and Cloud Transition EPIC 2001 ship data
03 LT 06 LT 09 LT Closed Open Transition
GO
ES I
R C-
band
rad
ar
03 LT 06 LT 0715 LT 08 LT 09 LT
Comstock et al. 2007
sunrise
![Page 8: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/8.jpg)
VOCALS 2008
C-130 data
Wood et al. 2011
Sunrise 1042 UTC
![Page 9: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/9.jpg)
sunset sunset sunrise sunrise sunset
dBZ
Vr
NOAA/ESRL vertically-pointing Cloud Radar data 13 -14 Nov 2008, longitude ~76° W
300 m
Hei
ght (
km)
Hei
ght (
km)
UTC (hr) →
dow
n up
![Page 10: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/10.jpg)
VOCALS REx (Southeast Pacific, Oct-Nov 2008)
• C-band radar data – Precipitation
Information – Every 3 minutes – 60 km radius around
ship – 250 m resolution
NOAA ship Ronald H. Brown
• GOES IR Satellite – Cloud Fraction Info – Every 30 min
![Page 11: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/11.jpg)
11
GOES VIS with ship radar reflectivity overlaid
120 km
![Page 12: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/12.jpg)
C-band radar- observed drizzle Areal rain rate and the number of drizzle cells peak between 0-3 am and are at their lowest values between 2-5 pm.
Burleyson et al. (2013)
![Page 13: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/13.jpg)
Diurnal cloud amount changes and lack of sensitivity to areal precipitation
>5% CF decrease overnight (6pm to 6am) in only 4 out of 289 1-hr samples (1%) and 9 out of 306 3-hr samples (3%)
![Page 14: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/14.jpg)
Cloud condition categories Scattered: < 75% CF
Broken: 75%<CF<100%
Overcast: CF=100%
Transition = cloud cover is changing in time
![Page 15: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/15.jpg)
19.5 dBZ +-1.25 dB
Day Time
Night Time
Median 85th %
+8 dB
25 dBZ +4.5 dB
Drizzle cell peak intensities
Scattered Broken Overcast Transition
![Page 16: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/16.jpg)
19.5 dBZ +-1.25 dB
Day Time
Night Time
Median 85th %
Drizzle cell peak intensities
Scattered Broken Overcast Transition
![Page 17: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/17.jpg)
Cumulative Frequency of Precip Area vs Cloud Event (day/night)
Night
Becomes Overcast, Remains Broken Remains Overcast, Becomes Broken
Occurred with less average precipitation area
![Page 18: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/18.jpg)
Cumulative Frequency of Precip Area vs Cloud Event (day/night)
Occurred with less average precipitation area
Occurred with more average precipitation area
Night Day
Becomes Overcast, Remains Broken Remains Overcast, Becomes Broken
![Page 19: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/19.jpg)
Drizzle does not appear to be a primary driver for decreasing cloud fraction
![Page 20: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/20.jpg)
Importance of Starting Cloud Fractions (Day: Dawn to Dusk)
DAWN DUSK DAWN DUSK
![Page 21: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/21.jpg)
Importance of Starting Cloud Fractions (Night: Dusk to Dawn)
DUSK DAWN DUSK DAWN
![Page 22: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/22.jpg)
Conclusions • Anecdotal examples can be found for a variety of
cloud fraction and precipitation area conditions – Cloud fraction increasing with/without precipitation – Cloud fraction decreasing with/without precipitation – Cloud fraction persisting with/without precipitation
• At night: – Overcast conditions with/without precipitation usually
do not break up – Overcast cloud breakup can occur without precipitation
• During the day: – Clouds with larger precipitation areas tend to maintain
their existing cloud fraction (likely thicker clouds) – Clouds that change cloud fraction have less
precipitation area (likely thinner clouds)
![Page 23: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/23.jpg)
Conclusions • At 100-300 km and < 5 hour scales:
– Drizzle and cloud fraction co-varying with diurnal cycle of solar radiation
– Drizzle is neither necessary nor sufficient for reducing cloud fraction overnight
– Impact of overnight drizzle reducing cloud fraction is very small (< 3% occurrence)
![Page 24: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/24.jpg)
Wyant et al. 2014 Model Intercomparison
![Page 25: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/25.jpg)
Wyant et al. 2014
![Page 26: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/26.jpg)
Models have difficulty with the amplitude and phase of the diurnal cycle of low clouds
Wyant et al. 2010
![Page 27: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/27.jpg)
Results – Diurnal Cycle of Cloud Fraction
Earlier breakup of the cloud and larger amplitude diurnal cycles are observed
in low cloud fraction regions and in deeper boundary layers. Burleyson (2013)
![Page 28: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/28.jpg)
Observed to vary with diurnal cycle in marine Sc
• Long Wave and Short Wave radiation fluxes • Cloud fraction • Subcloud turbulent moisture transport
– Profiles of vertical velocity variance, potential temperature, water vapor mixing ratio, horizontal wind, dew point temp
– Wind direction
• Cloud top height, cloud base height, cloud depth, Liquid Water Path
• Number of drizzle cells, drizzle area, areal average rain rate
![Page 29: Questioning the importance of the cloud lifetime effect: The relative roles … · 2019-08-21 · Questioning the importance of the cloud lifetime effect: The relative roles of drizzle](https://reader035.vdocuments.net/reader035/viewer/2022070713/5ed08d3f879769460e29fcdb/html5/thumbnails/29.jpg)
Not observed to vary with diurnal cycle in southeast Pacific marine Sc
• Near surface aerosol concentration • Near surface wind speed • Conditional rain rate • Proximity of drizzle cells