Emerging Technology for Satellite Remote Sensing of Boundary Layer Clouds and their Environment

Transcription

1 Emerging Technology for Satellite Remote Sensing of Boundary Layer Clouds and their Environment Matt Lebsock (NASA-JPL) Contributors: Chi Ao (NASA-JPL) Tom Pagano (NASA-JPL) Amin Nehir (NASA-Langley)

2 Where are we now? A-Train provides the definitive remote sensing data set for boundary layer clouds Vertical profiles from CloudSat/CALIPSO Large scale context: MODIS Precipitation: CloudSat Liquid Water Path/Content: MODIS/AMSR/CloudSat Very limited thermodynamics from AIRS Constellation flying has been an unparalleled success The A-Train is old: Maintaining the cloud-profiling data record is critical EarthCARE will only provide brief continuity

3 Radar Clouds: Limitations and Future Fixes Radar has marginal sensitivity. FIX: Bigger antenna, Lower orbit, Higher transmit power Surface clutter contaminates radar below 1 km FIX: Proven advanced pulse compression techniques Nadir sampling limits spatial context FIX: Electronic scanning now possible Poor quantitative microphysical retrievals (LWC, Optical Depth, Effective radius). FIX: Add radiometric channel to radar; Add coincident multi-angle imager

4 Radar-Radiometer Synergy - It is possible to build a radar with high precision (colocated) passive radiometric channels. - This is a key constraint on cloud retrievals allowing precise separation of cloud and precipitation water path. - Example shows the current capability with CloudSat (precision ~ 4K). Needed precision is < 0.5 K.

5 Surface Clutter in Radar RainCube Pulse Compression performance: confirmed RainCube, a Ka-band Precipitation Radar in a 6U CubeSat Rain-Cube pulse compression demonstrates eliminating clutter within 500 m of the surface & 250 m range resolution.

6 Boundary Layer Thermodynamics & Clouds Marine Boundary Layers tend to have relatively simple, repeatable thermodynamic structures. The cloud cover is essentially a product of these these structures. Is the cloud problem a temperature/humidity problem? What is needed: Higher resolution (vertical & horizontal) thermodynamics. Key to improving understanding of clouds.

7 CubeSat & SmallSat PBL IR Sounding Higher Spatial Resolution IR Sounding is Key to Enabling Studies of PBL Moist Thermodynamic Processes Provides: (1) cloud free FOV and (2) horizontal variability scales. CubeSat Solution Offers 500m GSD CubeSat High-resolution Infrared PBL Sounder (CHIRPS) SmallSat Solution Offsers 100m GSD Boundary Layer Infrared Sounding Spectrometer (BLISS) Performance: Spatial: Orbit: 600 km, GSD: 500 m, FOV: 48.5 km (±2.31 ) Spectral: cm -1, Resolution: cm -1 NEdT: < 0.5K at 280K 6U CubeSat, 14 kg, 25W Performance: Spatial: Orbit: 705 km, GSD: 100 m, FOV: 25 km (±1.2 ) Spectral: cm -1, Resolution: cm -1 NEdT: < 0.25K at 280K 0.4 x 0.4 x 0.7 m, 50 kg, 50 W 7

8 Future of PBL Sensing from GNSS-RO Improved Coverage: Expanding constellation of satellites. COSMIC-2A alone will produce ~6000 soundings in the tropics (> 6x COSMIC-1). 24 hour coverage from COSMIC Courtesy of NSPO Taiwan Improved Penetration: COSMIC-2 carries the advanced TriG receiver from JPL with beam form antenna technology. Median profile depth in the tropics will improve from 1 km to < 200 m Improved Retrieval: negative bias under very strong inversion layer (Sc regions) can be significantly reduced using a multisensor approach Significant improvement within the PBL by optimally combining RO and PW from AMSR-E Wang et al., Atmos. Meas. Tech., 2017

9 Water Vapor DIAL: Current and Future DIAL is self calibrating LASE Airborne DIAL Measurements Long-standing heritage of over 30 years in airborne process studies Extensive validation shows high accuracy and precision throughout troposphere Next generation airborne simulators currently being developed as a stepping stone to space ER2 Next Generation DIAL DIAL Sonde Future Mission DIAL Sonde Model Input DIAL Mission Enabled Through Technology Advancements Space-Based DIAL Performance Simulation WALES Instrument Simulation

10 Differential Absorption Radar: In Cloud Humidity (A)$ Microwave analogue of DIAL using 183 GHz absorption feature. Emerging technological capabilities. NASA funded technology development will fly 2019 (aircraft) Requires radio-frequency licensing. Vested interests discourage new use of spectrum. Advocacy from science community needed to motivate space agencies to support instrument development $ km RICO water vapor gm Radar Simulator + LES demonstrate the utility of DAR for: 1. in cloud humidity sounding, which is a good proxy for all-sky humidity profile 2. High-resolution, all-weather, column water vapor (using surface reflectance) for estimating smallscale humidity variance. *This is a low-transmitpower -> low-cost observation km km Z 0, km db

11 Recommendations Simultaneous observations (e.g. A-Train) of cloud/thermodynamics should be prioritized. International collaborations and constellation flying must be pursued, including small satellite platforms, to maintain the data record. Next-generation cloud radar with ~4x increased sensitivity, ~2x vertical resolution, decreased surface clutter, scanning, and radiometry is feasible today. Increased vertical/horizontal resolution of boundary layer thermodynamics is needed. 500 m vertical and 2 km horizontal should capture gross structures and their regional variability. Active profiling methods (lidar/radar) for water vapor are within reach but requires additional technology maturation to reach space and access to spectral bandwidth (radar).