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Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS)

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Microphysical imprint of entrainment in warm cumulus
(2013) Small, Jennifer D.; Chuang, Patrick Y.; Jonsson, Haflidi H.; Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS); Meteorology
We analyse the cloud microphysical response to entrainment mixing in warm cumulus clouds observed from the CIRPAS Twin Otter during the GoMACCS field campaign near Houston, Texas, in summer 2006. Cloud drop size distributions and cloud liquid water contents from the Artium Flight phase-Doppler interferometer in conjunction with meteorological observations are used to investigate the degree to which inhomogeneous versus homogeneous mixing is preferred as a function of height above cloud base, distance from cloud edge and aerosol concentration. Using four complete days of data with 101 cloud penetrations (minimum 300m in length), we find that inhomogeneous mixing primarily explains liquid water variability in these clouds. Furthermore, we show that there is a tendency for mixing to be more homogeneous towards the cloud top, which we attribute to the combination of increased turbulent kinetic energy and cloud drop size with altitude which together cause the Damko¨ hler number to increase by a factor of between 10 and 30 from cloud base to cloud top. We also find that cloud edges appear to be air from cloud centres that have been diluted solely through inhomogeneous mixing. Theory predicts the potential for aerosol to affect mixing type via changes in drop size over the range of aerosol concentrations experienced (moderately polluted rural sites to highly polluted urban sites). However, the observations, while consistent with this hypothesis, do not show a statistically significant effect of aerosol on mixing type.
Airborne Flux Measurements of BVOCs above Californian Oak Forests: Experimental Investigation of Surface and Entrainment Fluxes, OH Densities, and Damköhler Numbers
(2013-10) Karl, T.; Misztal, P.K.; Jonnson, H.H.; Shertz, S.; Goldstein, A.H.; Guenther, A.B.; Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS); Meteorology
Airborne flux measurements of isoprene were performed over the Californian oak belts surrounding the Central Valley. The authors demonstrate for the first time 1) the feasibility of airborne eddy covariance measurements of reactive biogenic volatile organic compounds; 2) the effect of chemistry on the vertical transport of reactive species, such as isoprene; and 3) the applicability of wavelet analysis to estimate regional fluxes of biogenic volatile organic compounds. These flux measurements demonstrate that instrumentation operating at slower response times (e.g., 1–5 s) can still be used to determine eddy covariance fluxes in the mixed layer above land, where typical length scales of 0.5–3km were observed. Flux divergence of isoprene measured in the planetary boundary layer (PBL) is indicative of OH densities in the range of 4–7 3 106 molecules per cubic centimeter and allows extrapolation of airborne fluxes to the surface with Damk€ohler numbers (ratio between the mixing time scale and the chemical time scale) in the range of 0.3–0.9. Most of the isoprene is oxidized in the PBL with entrainment fluxes of about 10% compared to the corresponding surface fluxes. Entrainment velocities of 1–10 cm s21 were measured. The authors present implications for parameterizing PBL schemes of reactive species in regional and global models.
Instrument List
(2014-06-11) Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS); Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS)
Airborne flux measurements of biogenic isoprene over California
(2014) Misztal, P.K.; Karl, T.; Weber, R.; Jonsson, H.H.; Guenther, A.B.; Goldstein, A.H.; Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS); Meteorology
Biogenic isoprene fluxes were measured onboard the CIRPAS Twin Otter aircraft as part of the California Airborne Biogenic volatile organic compound (BVOC) Emission Research in Natural Ecosystem Transects (CABERNET) campaign during June 2011. The airborne virtual disjunct eddy covariance (AvDEC) approach used measurements from a proton transfer reaction mass spectrometer (PTR–MS) and a wind radome probe to directly determine fluxes of isoprene over 7400 km of flight paths focusing on areas of California predicted to have the largest emissions. The fast Fourier transform (FFT) approach was used to calculate fluxes of isoprene over long transects of more than 15 km, most commonly between 50 and 150 km. The continuous wavelet transformation (CWT) approach was used over the same transects to also calculate instantaneous isoprene fluxes with localization of both frequency and time independent of non-stationarities. Fluxes were generally measured by flying consistently at 400m±50m (a.g.l.) altitude, and extrapolated to the surface according to the determined flux divergence determined in the racetrack-stacked profiles. The wavelet-derived surface fluxes of isoprene averaged to 2 km spatial resolution showed good correspondence to basal emission factor (BEF) land-cover data sets used to drive BVOC emission models. The surface flux of isoprene was close to zero over Central Valley crops and desert shrublands, but was very high (up to 15 mgm−2 h−1) above oak woodlands, with clear dependence of emissions on temperature and oak density. Isoprene concentrations of up to 8 ppb were observed at aircraft height on the hottest days and over the dominant source regions.
Twin Otter - CIRPAS - NPS
(2022-04-28) Woods, Roy; Jonsson, Halflidi; Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS); Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS); Earth Science Project Office (ESPO) at NASA
MWR-05XP Mobile Phased Array Weather Radar
(2014-06-11) Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS); Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS)
The NPS/CIRPAS Weather Radar Project objective is to develop the technology for adding a parallel weather processor capability to tactical military radars and to develop an advanced scientific instrument for investigation of atmospheric phenomena and other various types of research. The payoff to the military will be the integration of current weather data into the tactical radar picture. The payoff to the science community will be the availability of an advanced instrument for investigation of atmospheric phenomena.
Determination of the Transmission Efficiency of an Aircraft Aerosol Inlet
(2005) Hegg, Dean A.; Covert, David S.; Jonsson, Haflidi; Covert, Paul A.; Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS); Naval Postgraduate School (U.S.); Meteorology
Data are reported for both airborne and wind tunnel testing of the aerosol inlet on the CIRPAS Twin Otter research aircraft. Though utilizing different instrumentation and assumptions, results from the two test venues show broad agreement. The roll off in transmission efficiency of the inlet under standard flight conditions starts at ∼3.5 μm but plateaus at 5.5 μm particle diameter at a value slightly in excess of 0.6. This value persists to the upper limit of the test range at 9 μmand is likely due to the sub-isokinetic aspiration flow of the inlet.
Ground Based Systems
(2014-06-11) Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS); Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS)
The Naval Postgraduate School and the Navy’s Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) in collaboration with ProSensing Inc. has modified an X-Band tactical radar system to add a weather observation mode. The new system was named MWR-05XP (Mobile Weather Radar, 2005 X-Band, Phased Array) and is the first mobile, electronically scanned phased array radar developed for weather sensing applications. Key system parameters of the MWR-05XP rapid scanning radar system are summarized. As part of the modification, ProSensing developed a state-of-the-art PC based weather processor (WRP), which provides radar control, data acquisition, signal processing, real-time data display. Processing algorithms provide estimates of reflectivity, average radial velocity and velocity spread for distributed targets.
Pelican
(2014-06-11) Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS); Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS)
The Pelican is a highly-modified Cessna 337, O2, Skymaster originally developed by the Office of Naval Research for low-altitude, longendurance atmospheric and oceanographic sampling. Through an SBIR program between Zivko Aeronautics and GA, the air vehicle was configured to operate as a true Predator UAV surrogate for the U.S. Navy. Pelican has supported several military exercises that require a UAV capability for the troops to work with, but where a real UAV wasn't practical to operate due to FAA restrictions. With Pelican, the US Military can realistically train with capabilities very close to those of the UAV's that they will work with on the battlefield.
Precipitation effects of giant cloud condensation nuclei artificially introduced into stratocumulus clouds
(2015) Jung, E.; Albrecht, B.A.; Jonsson, H.H.; Chen, Y.-C.; Seinfeld, J.H.; Sorooshian, A.; Metcalf, A.R.; Song, S.; Fang, M.; Russell, L.M.; Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS); Meteorology
To study the effect of giant cloud condensation nuclei (GCCN) on precipitation processes in stratocumulus clouds, 1–10 μm diameter salt particles (salt powder) were released from an aircraft while flying near the cloud top on 3 August 2011 off the central coast of California. The seeded area was subsequently sampled from the aircraft that was equipped with aerosol, cloud, and precipitation probes and an upward-facing cloud radar. During post-seeding sampling, made 30–60 min after seeding, the mean cloud droplet size increased, the droplet number concentration decreased, and large drop (e.g., diameter larger than 10 μm) concentration increased. Average drizzle rates increased from about 0.05 to 0.20mmh-1, and the liquid water path decreased from about 52 to 43 gm-2. Strong radar returns associated with drizzle were observed on the post-seeding cloud-base levelleg flights and were accompanied by a substantial depletion of the cloud liquid water content. The changes were large enough to suggest that the salt particles with concentrations estimated to be 10-2 to 10-4 cm-3 resulted in a four-fold increase in the cloud-base rainfall rate and depletion of the cloud water due to rainout. In contrast, a case is shown where the cloud was already precipitating (on 10 August) and the effect of adding GCCN to the cloud was insignificant.