SCM

The objective of this experiment was to evaluate strategies for conducting SCM experiments at Barrow, using the Aerosonde and the NOAA ATDD Long Easy aircraft.

Several weeks before the planned start of the IOP, we were informed that the Long Easy would not be able to participate because of difficulties in identifying a pilot. The Long Easy was expected to make transects of surface flux measurements, as well as to conduct flight patterns to begin investigating some of the site-specific science questions that were not addressed during SHEBA. The absence of the Long Easy was not deemed too serious for the central objectives of the SCM IOP.

Activity Summary

AEROSONDE SUMMARY

Before going into the field with the Aerosonde, we were operating under the following constraints and known concerns: 1) strict flight patterns imposed by the FAA, primarily owing to the lack of a strobe light and transponder on the Aerosonde 2) the Aerosonde had not been tested at temperatures colder than -26C 3) temperatures in April were expected to be within range where icing conditions are expected.

Three Aerosonde flights were conducted. The first flight resulted in a crash after 10 hours owing to icing. The second and third flights, designed to avoid icing conditions, also resulted in crashes owing to engine problems. While the issues encountered do not represent insurmountable problems, there was no way to fix these problems in Barrow, and the project was terminated after these three flights.

We have identified several solutions to the problems encountered: 1) put strobe light and transponder on Aerosonde so it is not restricted to flying out of Barrow at low altitudes 2) a strategy has been developed for avoiding and leaving icing conditions, although this may compromise the mission if measurements are desired at altitudes where icing conditions prevail. 3) several deicing strategies are being considered. With the exception of applying wax to the aerosonde, these deicing will require modification to the Aerosonde platform. 4) a new fuel injected engine will be used in the Mark II Aerosonde (ready in 2000), which will eliminate the engine problems that were encountered.

For the three flights flown in the vicinity of Barrow, we highlight the following findings:

• substantial variability (vertical and horizontal) in atmospheric humidity (little horizontal temperature variability)
• The balloon sounding from Barrow was 1.5-2oC cooler than the Aerosonde observations at almost all levels.
• The thorough ground check of the aerosonde instruments and general agreement with the ARM soundings indicates problems with the Barrow NWS soundings.

CONCLUSIONS

Although we were not able to obtain atmospheric profile data surrounding Barrow, from which to construct a SCM dataset, we learned a considerable amount from this experience. At a cost of about $100K to ARM, this IOP was a valuable learning experience. Given the initial SCM experiences at SGP, we understand that this initial failure is not surprising or unexpected.

We believe that the Aerosonde remains a viable option for obtaining profiles of meteorological parameters in the vicinity of Barrow, to be used in future SCM IOPs. Additionally, if suitably instrumented, the Aerosonde has the potential to be a much safer platform than manned aircraft from which to obtain surface fluxes over the broken ice.

The alternative option for SCM IOPs is a manned aircraft flying a 100 km circle at high altitudes around Barrow, deploying dropsondes. We will cost out this option and compare carefully against an Aerosonde system that is fully capable of operating under conditions at Barrow.

All participants in springtime IOPs at Barrow agreed that the superb infrastructure in Barrow made conducting IOPs very easy. We note that once approved, it only took 6 months to put together the April SCM IOP at Barrow. This bodes very well for future IOPs at Barrow.

TOWARDS THE FUTURE

The most positive outcome of the SCM IOP was the considerable enthusiasm generated for use of Aerosondes at Barrow, by the ARM scientists involved, the Aerosonde group, and by the Barrow residents. This enthusiasm has motivated the preparation of a major proposal to NSF-OPP in response to an announcement for Opportunities for Long-Term Measurements in the Arctic, which explicitly targets remote/autonomous instruments.

If funded, this project would hopefully result in another Aerosonde attempt at Barrow in March 2000 to conduct the ARM SCM IOP mission, at little or no cost to ARM. The draft abstract of this proposal is given below (we are requesting funding for 5 yrs, approx $1M/yr).

Applications of Aerosondes to Long-Term Measurements of the Atmosphere and Sea Ice Surface in the Beaufort/Chukchi Sector of the Arctic Ocean

The Aerosonde is a small (15 kg) robotic aircraft that has been developed to make atmospheric measurements. The Aerosonde has flown twice in high latitudes: the first time was August 1998 the Aerosonde flew across the North Atlantic from Nova Scotia to Scotland; and the second was deployment of aerosondes from Barrow during April 1999 in support of the DOE ARM Single Column Model Experiment.

The Aerosonde is presently outfitted with a suite of instruments to measure atmospheric state parameters (e.g. temperature, humidity, winds), although future experiments with different instruments are being planned. Here we propose to develop a facility at Barrow for Aerosonde deployment and reconnaissance in the Arctic, to increase routine observational capability of the atmosphere and the ice/ocean surface in the Beaufort/Chukchi sector of the Arctic Ocean. Specifically we propose to:

1. establish a facility for aerosonde deployment and reconnaissance at Barrow

2. adapt the aerosonde design to be more robust and efficient for arctic applications

3. integrate additional miniature instruments into the aerosonde system (e.g. radiometers, laser altimeter, videocamera, chemistry measurements)

4. regularly deploy the aerosondes to measure atmospheric state and surface characteristics

5. set up a data dissemination, distribution, and archiving system for the aerosonde data

6. work with operational modeling and remote sensing centers to assimilate these data into their analyses

7. collaborate/cooperate with any field projects in the area and provide support to any local scientific issues put forward by the Barrow Arctic Science Consortium.

The primary targets for the observations are the following applications:

1. Routine measurement of atmospheric state for assimilation into numerical weather prediction (NWP) model analyses. This would substantially improve the analyses and forecasts in this region of the arctic. Note that NWP analyses are the main source of large scale atmospheric information used for diagnostic studies, to force regional atmospheric models, and to provide surface forcing for ice/ocean models

2. Measurement of surface radiative fluxes and surface sea ice characteristics (e.g. surface temperature (including determination of open water and thin ice), melt pond fraction, and possibly ice thickness distribution. These measurements would be used to evaluate sea ice models and could be incorporated into the RGPS analysis system for improved product of sea ice characteristics.

Timeline