1. Long-term Synthesis of ARM Millimeter Cloud Radar and
Micropulse Lidar Observations
Karen Johnson1, Michael Jensen1, Pavlos Kollias2, Jennifer Comstock3, Eugene Clothiaux4, Mark Miller5
1Brookhaven National Laboratory Pennsylvania State University McGill University 4Pacific Northwest National Laboratory Rutgers University
1) Multi-Year Radar and Lidar Observations
2) ARM’s Best-Estimate
Radar-Lidar Synthesis:
ARSCL
The Atmospheric Radiation Measurement (ARM) program has ongoing multi-year records of
Cloud Boundaries
Hydrometeor Reflectivity
Vertical Velocity, more…
based on synthesized measurements from vertically pointing
Millimeter Cloud Radar (35 GHz, 95 GHz)
Micropulse Lidar
Ceilometer
Black Forest,
Germany
(2007)
North Slope
of Alaska
(since 1998)
Southern
Great Plains
(since 1996)
ARM routinely processes radar, lidar, ceilometer and surface measurements from each site to produce a value-added product, ARSCL (Active Remote Sensing of CLouds), which provides cloud boundaries, best-estimate hydrometeor reflectivities, vertical velocities and spectrum widths.
China (2008)
Manus, PNG
(since 1996)
Nauru Island
(since 1998)
Darwin
(since 2002)
ARSCL Examples
Niamey, Niger
(2006)
ARM has 5 fixed global sites and two ARM Mobile Facility deployments (to-date).
Southern Great Plains
Niamey, Niger
Height (km)
Time (hours) 16 24
95 GHz Radar
Reflectivity
Height (km)
Time (hours) 24 14
dBZ
35 GHz Radar
Reflectivity
Radar modes are merged and artifacts removed.
Data are freely available! 14 16 18 12 10 8
Radar + Lidar
3) Cirrus Clouds as Detected by Radar and/or Lidar
Cloud Top Heights
Radar-only
Lidar-only + +
Heights (km)
Micropulse Lidar
Height (km)
Time (hours) 24 16
Log10(power)
Micropulse Lidar
Height (km)
Time (hours) 16 24
Log10(power)
Fewer Lidar mid-level clouds due to attenuation
The ARSCL product allows us to compare radar vs. lidar cloud detection.
Right is a typical monthly histogram of radar-only vs. lidar-only vs. radar-plus-lidar cirrus clouds detections (above 6km).
Below, heating rates were computed using SBDART to assess the radiative impact of cirrus missed due to radar-only or lidar-only detections.
Radar misses high cloud
Lidar backscatter is converted into a lidar cloud mask. 6 14 16 18 12 10 8 6
Radar-only
Radar + Lidar
Lidar-only
Cloud Base Heights
Heights (km)
Best-Estimate Reflectivity plus Cloud Boundaries
Height (km)
Time (hours) 24 16
Height (km)
Time (hours) 24 14
dBZ
x 104
Sample Cloud Masks for Niamey, Niger
Number of Occurrences
Radar, lidar and ceilometer are combined to distinguish cloud and precipitation, 14 12 10
Time (9 hours)
Lidar-only detection
Radar-only detection
Radar + Lidar Detection
Radar only, Lidar missing
Clear
Height (km)
eliminate radar clutter, add cloud seen by only lidar, and extend lidar cloud tops as detected by radar.
Time (9 hours)
Time (9 hours)
Cloud Mask showing Instrument Source
IR Lidar
Solar Lidar
Lidar-only
detections
Upper cloud seen by radar only
IR Radar
Solar Radar
Time (hours) 12 24
Height (km) 16 8
Lidar-Detected
Cirrus Heating
In Section 3) at left, we examine the value of radar vs. lidar vs. both in detecting cirrus.
Additional
Radar-Detected
Cirrus Heating
Additional
Lidar-Detected
Cirrus Heating
Clutter
Lidar only, Radar missing
Radar only, Lidar missing
Lidar-only detection
Radar-only detection
Radar + Lidar Detection
Clear
Missing Radar and Lidar
Significant Heating Rates associated with Undetected Cirrus