Report on the workshop for in situ airborne instrumentation: addressing and solving measurement problems in ice clouds

Despite the progress that has been made in the last twenty years towards understanding the formation and evolution of clouds and their impact on weather and climate, serious gaps remain, many of which are associated with measurement uncertainties and limitations. Unraveling the complex relations between aerosols and cloud particles is hindered by the lack of adequate instrumentation for identifying the primary modes of ice initiation, discriminating liquid water from ice, identifying crystal shapes segregated by size, determining the chemistry of cloud hydrometeors and measuring the optical properties of single and ensembles of cloud particles, to name just some of the problems facing the atmospheric science community. Part of the problem is due to the difficulties associated with making in situ measurements from airborne platforms where the airframe and instrument body can influence the flow and generate artificial particles from impaction and shattering. Another part of the problem is that there are no universally accepted standards for calibrating instruments and assuring strict quality control, nor for processing the data. The lack of standardizations impedes our capacity to understand the significant differences that are often observed in the cloud properties measured by different instruments on the same platform.

In order to address the needs of the cloud physics community for improving our ability to measure the properties of clouds, particularly those containing ice, a workshop will be held during which more than 30 international experts will convene to address the many issues that relate to airborne, in situ measurements. The primary goal of this meeting is to provide a clear guide that can be utilized by users of cloud microphysical measurements, developers of airborne instruments and funding agencies that support both groups that have overlapping interests.

The specific objectives of this workshop, to be held the 25 and 26th of June, 2010 are:

1) To identify critical, unresolved scientific questions related to the formation and evolution of ice in clouds. 2) To summarize the uncertainties and limitations of in situ sensors related to measurements of ice cloud properties. 3) To assess and evaluate potential approaches that reduce the uncertainties and minimize the limitations, including a review of emerging technologies. 4) To recommend methods for standardizing calibration and quality control. 5) To discuss and evaluate standardization of data processing methodologies. 6) To discuss whether and how to rate the quality of earlier measurements reported in the literature with respect to the current state of knowledge regarding measurement limitations and uncertainties.

Each participant has been given specific instructions as to what they are to prepare prior to the meeting. They will be tasked with giving an oral presentation at the meeting and will be required to submit a written summary that will be integrated into the workshop report. This report will be summarized at the Cloud Physics Conference, published in its entirety as an NCAR Technical Note then submitted for publication in BAMS as a meeting summary.