Fall 1997 Cloud IOP

15 September 1997 - 5 October 1997

Lead Scientist: Gerald Mace

Observatory: sgp, sgp

Goals: The focus of the Cloud IOP is to generate data sets to validate and develop retrieval algorithms. Specific issues include:

  • Constraint of error bars
  • Determination of what algorithms can be implemented
  • Calibration of the CART MMCR and guest radars
  • Use of IOP as a tool to learn things to apply to day-to-day operational data streams

Activity Summary

The primary objective of the Cloud IOP was to generate a multi-platform data set that can be used as validation for cloud property retrieval algorithms that are being implemented on the operational MMCR data stream. Within this primary objective, secondary objectives included: 1) quantification of the uncertainty associated with the various algorithms, 2) provide absolute calibration and intercalibration for the millimeter radars used in cloud research (including the CART MMCR), and 3) provide guidance on the operational modes of the CART MMCR. All of these objectives were addressed with varying degrees of success during the course of the IOP.

The MMCR was operated in a number of new operational modes, including the collection of Doppler spectra, with no identifiable negative impact on general MMCR data quality. A new set of operational modes was devised to maximize the scientific utility of the full data stream. A mode was added to provide high vertical resolution with sufficient sensitivity for lower and middle tropospheric water clouds. A mode was also added for identification of certain ambiguities in the other modes.

It was desired to sample a full spectrum of cloud types and meteorological conditions both in situ and with surface instruments. Cloud types of interest included single-layer liquid phase, ice-phase, and mixed-phase clouds, as well as multi-layered conditions. To some degree, all of these cloud types were sampled. The weather pattern during the first half of the IOP was very conducive to high-based mixed-phase clouds below cirrus. The Citation and the King Air flew several missions in these situations. Dual aircraft missions were also conducted in which the Citation sampled cirrus and the King Air worked the mixed phase clouds. The King Air also conducted several flights in liquid phase stratocumulus clouds near the middle of the IOP. A diversity of microphysical characteristics in stratocumulus clouds was observed. The Gulfstream-1 also performed cloud-related missions in several stratocumulus events. The opportunity to sample single layer cirrus was limited to a single case associated with the remains of Hurricane Nora. While this was the only cirrus case, it did appear to be exceptional with extraordinary optical displays in a persistent overcast layer.

Given the diversity of cloud types sampled during the IOP, the analysis of this data set will continue for some time. Web pages are being developed that summarize each aircraft flight having a significant data collection period.

Development of these summaries will facilitate the use of the data by the wider community. Beyond the web pages the data will be used for their intended purpose of validating retrieval algorithms as they are implemented. Basic scientific research will also be conducted since several of the cases were unique and very well sampled by the surface and ground-based instruments. The Cloud Working Group intend to maintain a close collaboration with the Shortwave Radiation IOP group as well since the synergy between the two groups was evident during the IOP.

While analysis of the data collected during the IOP will dictate the need for future Cloud IOPs, it is certain that this exercise will need to be repeated in the future with an emphasis on cirrus clouds. It is also evident that conducting a Cloud IOP during late September is not advisable in the future. This particular IOP succeeded largely due to anomalously abundant moisture in the eastern Pacific.

Guest ground-based instrumentation included the University of Utah 95 GHz Doppler radar system polarization diversity lidar and time lapse video, Penn State University millimeter cloud radar, lidar, sunphotometer, and NFOV infrared radiometer, University of Massachusetts dual 35/95 GHz scanning cloud radar, University of Utah polarization diversity lidar, Colorado State University beam filter infrared radiometer, and NCAR balloon-borne Formvar ice particle replicator. Critical ARM instrumentation included the MMCR, MPL, BLC, VCEIL, AERI, MWR, and BBSS.

All three aircraft carried standard meteorological sensors, along with devices to measure cloud droplet number concentration and size distribution, cloud liquid water content, and cloud condensation nuclei number. The Citation and King Air carried additional sensors to measure cloud and large particles, supercooled liquid water content, and radiometric properties. The Citation was equipped with a time lapse camera and video, while the King Air's payload included the Wyoming 95 GHz cloud radar. In addition, the Twin Otter carried the DOE 7-channel microwave radiometer (DoER) and the 5-channel millimeter-wave imaging radiometer (MIR). Data from these devices should complement those of the cloud radars, especially in the correction path attenuation due to clouds and water vapor near 90 GHz. These data should also help develop cloud and water vapor retrievals using passive microwave/millimeter-wave frequencies from 20-325 GHz.

Citation flights, mainly into cirrus and higher mid-level clouds, occurred during the day on September 16, 17, 19, 26, and during some of its Water Vapor IOP nighttime missions. King Air flights, primarily into mid and lower level cloud layers, were made on September 16, 19, 20, 23, 24, and also during parts of its Water Vapor IOP nighttime missions. The Gulfstream flew cloudy air missions, from 500-17,000 ft. AGL, on September 21, 24, and 25. One NCAR ice replicator sonde flight was made into an interesting cirrus field on September 26. This particular day produced some unusual optics that were of interest to all of the IOPs. This flight was seen as an augmentation to the Citation in situ cirrus missions since ice water contents derived from the standard probes are generally uncertain by a factor of two. Additionally, the microphysical information to be gleaned from an aircraft mounted replicator is often obscured by the destruction of the crystal habits on impact. The replicator radiosondes bypass these difficulties. Although the launch that occurred provided only a single profile through a cirrus system, the data should provide an important check on the reliability of the microphysical data collected that day by the in situ aircraft.

Timeline

2003

Joseph E and Q Min. 2003. "Assessment of multiple scattering and horizontal inhomogeneity in IR radiative transfer calculations of observed thin cirrus clouds." Journal of Geophysical Research: Atmospheres, 108(D13), 10.1029/2002jd002831.

Sassen K, WP Arnott, DO Starr, GG Mace, Z Wang, and MR Poellot. 2003. "Midlatitude Cirrus Clouds Derived from Hurricane Nora: A Case Study with Implications for Ice Crystal Nucleation and Shape." Journal of the Atmospheric Sciences, 60(7), 10.1175/1520-0469(2003)060<0873:mccdfh>2.0.co;2.

2002

Liou KN, SC Ou, Y Takano, J Roskovensky, GG Mace, K Sassen, and M Poellot. 2002. "Remote sensing of three-dimensional inhomogeneous cirrus clouds using satellite and mm-wave cloud radar data." Geophysical Research Letters, 29(9), 10.1029/2002gl014846.

2001

McFarquhar GM, R Somerville, SF Iacobellis, and P Yang. 2001. Sensitivities of SCM models to improved parameterizations of cloud-radiative interactions for tropical cirrus. In Preprint from the Twelfth Symposium on Global Change and Climate Variations, Albuquerque, New Mexico: American Meteorological Society.

2000

Fu Q, B Carlin, and G Mace. 2000. "Cirrus horizontal inhomogeneity and OLR bias." Geophysical Research Letters, 27(20), 10.1029/2000gl011944.

Liu Y and PH Daum. 2000. "Spectral dispersion of cloud droplet size distributions and the parameterization of cloud droplet effective radius." Geophysical Research Letters, 27(13), 10.1029/1999gl011011.

Dong X, P Minnis, TP Ackerman, EE Clothiaux, GG Mace, CN Long, and JC Liljegren. 2000. "A 25-month database of stratus cloud properties generated from ground-based measurements at the Atmospheric Radiation Measurement Southern Great Plains Site." Journal of Geophysical Research: Atmospheres, 105(D4), 10.1029/1999jd901159.

Ivanova D, DL Mitchell, WP Arnott, and MR Poellot. 2000. A GCM Parameterization of Bimodal Size Spectra for Mid-latitude Cirrus Clouds. In Tenth ARM Science Team Meeting Proceedings, Ed. by N. Burleigh and D. Carrothers, Richland, WA: U.S. Department of Energy.

Ghan SJ, U Lohmann, J Hudson, MH Zhang, and X Dong. 2000. Use of ARM Measurements to Evaluate Droplet Number Prediction in Single-Column Models. In Tenth ARM Science Team Meeting Proceedings, Ed. by N. Burleigh and D. Carrothers, Richland, WA: U.S. Department of Energy.

Daum PH and Y Liu. 2000. Parameterization of Cloud Droplet Effective Radius: Effects of Spectral Dispersion and Skewness of Cloud Droplet Size Distributions. In Tenth ARM Science Team Meeting Proceedings, Ed. by N. Burleigh and D. Carrothers, Richland, WA: U.S. Department of Energy.


View All Related Publications

Campaign Data Sets

IOP Participant Data Source Name Final Data
William Arnott Replicator Order Data
Eugene Clothiaux Radar/Lidar Order Data
Gerald Mace Radar Order Data
Michael Poellot Citation Order Data
Kenneth Sassen Lidar Order Data
Stephen Sekelsky CPRS Order Data