Water in the Pacific TTL during ATTREX 2013

Troy Thornberry1,2, Drew Rollins1,2, Ru-Shan Gao1, David Fahey1,2

1NOAA ESRL CSD and 2CIRES, University of Colorado

MMS, FCDP, and CPL teams

ATTREX Science Team Meeting • 24 October 2013

Average flight: 7790 nm 14300 km 24.4 hrs

ATTREX Flights

ATTREX Flights

TTL Profiles ±15° Latitude

Temperature and WV Structure of the TTL

CP Tropopause altitudes between 17 and 18 km on individual profiles

H2O MR < 5 ppm above 16.5 km and as low as 1.5 ppm

Saturation Potential Temperature

Saturated mixing ratios not observed above ~380 K potential temperature surface

Altitude of the 380 K surface typically ~17.5 km (87 hPa)

Cirrus clouds observed with both large supersaturations and subsaturations, although mean values close to 100%

RHi and Clouds

RHice climatology

From Krämer et al., ACP, 2009Data from FISH + FLASH/OJSTER, 9 missions, 1999-2006

Where does the ATTREX data fall?

From Krämer et al., ACP, 2009Data from FISH + FLASH/OJSTER, 9 missions, 1999-2006

• Within the envelope of previous measurements

• Temperatures reached not as cold as FISH has seen

ATTREX RF05

26-27 February

Cloud Physics Lidar

Longitude

High water content cloud 7 – 15°N 26-27 February 2013

FCDP Data, SPEC Inc., P. Lawson PI

Contrasting cirrus clouds 7 – 15°N 26-27 February 2013

Dehydration by sedimentation

• The larger diameter particles will fall much faster, leading to faster downward transport of water

• Both types of cloud particles fall much faster than typical ascent rates so should provide dehydration- Effect of observed supersaturations?

Can we use trajectories to inform the data?

• In situ data provides a snapshot in time

• Tracer species can provide information on air parcel history

• Possible to get direct dynamic information?

• Trajectories from Tao Wang, Texas A&M

• ERA interim reanalysis• isentropic coordinate

model with diabatic heating vertical transport

Can we use trajectories to inform the data?

Add calculated saturation H2O MR to look at potential dehydration history

Summary

Dehydration was likely occurring just below 380 K (~ 17.5 km) in the central and eastern Pacific boreal winter

TTL cirrus clouds varied significantly in ice crystal number and size and in supersaturation, yielding a wide range of dehydration potentials

ATTREX RHice observations fit within the envelope from previous studies (Krämer et al, 2009)

Trajectories provide a possibility to investigate the air parcel history and provide context to the snapshot of in situ measurements Tantalizing, but fraught…