26 research outputs found
Physical science research needed to evaluate the viability and risks of marine cloud brightening
Marine cloud brightening (MCB) is the deliberate injection of aerosol particles into shallow marine clouds to increase their reflection of solar radiation and reduce the amount of energy absorbed by the climate system. From the physical science perspective, the consensus of a broad international group of scientists is that the viability of MCB will ultimately depend on whether observations and models can robustly assess the scale-up of local-to-global brightening in today\u27s climate and identify strategies that will ensure an equitable geographical distribution of the benefits and risks associated with projected regional changes in temperature and precipitation. To address the physical science knowledge gaps required to assess the societal implications of MCB, we propose a substantial and targeted program of research-field and laboratory experiments, monitoring, and numerical modeling across a range of scales
Stratus Ocean Reference Station (20˚S, 85˚W) : mooring recovery and deployment cruise, R/V Ronald H. Brown Cruise 06-07, October 9–October 27, 2006
The Ocean Reference Station at 20°S, 85°W under the stratus clouds west of northern Chile is being maintained to provide ongoing,
climate-quality records of surface meteorology, of air-sea fluxes of heat, freshwater, and momentum, and of upper ocean temperature,
salinity, and velocity variability. The Stratus Ocean Reference Station (ORS Stratus) is supported by the National Oceanic and
Atmospheric Administrations (NOAA) Climate Observation Program. It is recovered and redeployed annually, with cruises that have
come between October and December.
During the October 2006 cruise of NOAA's R/V Ronald H. Brown to the ORS Stratus site, the primary activities where recovery of the
Stratus 6 WHOI surface mooring that had been deployed in October 2005, deployment of a new (Stratus 7) WHOI surface mooring at that
site, in-situ calibration of the buoy meteorological sensors by comparison with instrumentation pub on board by staff of the NOAA Earth
System Research Laboratory (ESRL, formerly ETL), and observations of the stratus clouds and lower atmosphere by NOAA ESRL. A
buoy for the Pacific tsunami warning system was also serviced in collaboration with the Hydrographic and Oceanographic Service of the
Chilean Navy (SHOA). The old DART (Deep-Ocean Assessment and Reporting of Tsunami) buoy was recovered and a new one deployed
which carried IMET sensors and subsurface oceanographic instruments. Argo floats and drifters were also launched and CTD casts
carried out during the cruise. The ORS Stratus buoys are equipped with two Improved Meteorological (IMET) systems, which provide
surface wind speed and direction, air temperature, relative humidity, barometric pressure, incoming shortwave radiation, incoming
longwave radiation, precipitation rate, and sea surface temperature. The IMET data are made available in near real time using satellite
telemetry. The mooring line carries instruments to measure ocean salinity, temperature, and currents. The ESRL instrumentation used
during the 2006 cruise included cloud radar, radiosonde balloons, and sensors for mean and turbulent surface meteorology. Stratus 7 also
received a new addition to its set of sensors: a partial CO2 detector from the Pacific Marine Environmental Laboratory (PMEL). Aerosol
measurements were also carried out onboard RHB by personnel of the University of Hawaii. Finally, the cruise hosted a teacher
participating in NOAA's Teacher at Sea Program.Funding was provided by the National Oceanic and Atmospheric Administration
under Grant No. NA17RJ1223
The Second ARM Training and Science Application Event : Training the Next Generation of Atmospheric Scientists
Non peer reviewe
Stratus Ocean Reference Station (20˚S, 85˚W), mooring recovery and deployment cruise R/V Ronald H. Brown cruise 05-05, September 26, 2005–October 21, 2005
The Ocean Reference Station at 20°S, 85°W under the stratus clouds west of northern Chile is being maintained to provide
ongoing, climate-quality records of surface meteorology, of air-sea fluxes of heat, freshwater, and momentum, and of upper ocean
temperature, salinity, and velocity variability. The Stratus Ocean Reference Station (ORS Stratus) is supported by the National
Oceanic and Atmospheric Administration’s (NOAA) Climate Observation Program. It is recovered and redeployed annually, with
cruises that have come between October and December. During the October 2005 cruise of NOAA’s R/V Ronald H. Brown to the
ORS Stratus site, the primary activities were recovery of the WHOI surface mooring that had been deployed in December 2004,
deployment of a new WHOI surface mooring at that site, in-situ calibration of the buoy meteorological sensors by comparison
with instrumentation put on board by staff of the NOAA Environmental Technology Laboratory (ETL), and observations of the
stratus clouds and lower atmosphere by NOAA ETL. The ORS Stratus buoys are equipped with two Improved Meteorological
(IMET) systems, which provide surface wind speed and direction, air temperature, relative humidity, barometric pressure,
incoming shortwave radiation, incoming longwave radiation, precipitation rate, and sea surface temperature. The IMET data are
made available in near real time using satellite telemetry. The mooring line carries instruments to measure ocean salinity,
temperature, and currents. The ETL instrumentation used during the 2005 cruise included cloud radar, radiosonde ballons, and
sensors for mean and turbulent surface meteorology. In addition, two technicians from the University of Concepcion collected
water samples for chemical analysis. Finally, the cruise hosted a teacher participating in NOAA’s Teacher at Sea Program.Funding was provided by the National Oceanic and Atmospheric Administration
under Grant No. NA17RJ1223 and the Cooperative Institute for Climate and Ocean Research (CICOR)
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A Motion-Stabilized W-Band Radar for Shipboard Observations of Marine Boundary-Layer Clouds
Cloud radars at X, Ka and W-bands have been used in the past for ocean studies of clouds, but the lack of suitable stabilization has limited their usefulness in obtaining accurate measurements of the velocity structure of cloud particles and the heights of cloud features. A 94 GHz (W-band) radar suitable for use on shipboard studies of clouds has been developed that is small and lightweight and can maintain the radar’s beam pointing in the vertical to reduce the affects of the pitch and roll of the ship. A vertical velocity sensor on the platform allows the effects of the ship’s heave to be removed from the measured cloud particle motions. Results from the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-Rex) field program on the NOAA vessel Ronald H. Brown demonstrate the improvements to the cloud measurements after the ship’s motion effects are removed. The compact design of the radar also makes it suitable for use in aircraft studies. The radar is being repackaged to fit in an aft bay of a NOAA P3 aircraft to observe sea-spray profiles during ocean storms.Keywords: VOCALS 2008, Shipboard motion stabilization, Marine boundary-layer clouds, Cloud rada
Aerosol meteorology of Maritime Continent for the 2012 7SEAS southwest monsoon intensive study - Part 2: Philippine receptor observations of fine-scale aerosol behavior
Abstract. The largest 7 Southeast Asian Studies (7SEAS) operations period within the Maritime Continent (MC) occurred in the August–September 2012 biomass burning season. Data included were observations aboard the M/Y Vasco, dispatched to the Palawan Archipelago and Sulu Sea of the Philippines for September 2012. At these locations, the Vasco observed MC smoke and pollution entering the southwest monsoon (SWM) monsoonal trough. Here we describe the research cruise findings and the finer-scale aerosol meteorology of this convectively active region. This 2012 cruise complemented a 2-week cruise in 2011 and was generally consistent with previous findings in terms of how smoke emission and transport related to monsoonal flows, tropical cyclones (TC), and the covariance between smoke transport events and the atmosphere's thermodynamic structure. Biomass burning plumes were usually mixed with significant amounts of anthropogenic pollution. Also key to aerosol behavior were squall lines and cold pools propagating across the South China Sea (SCS) and scavenging aerosol particles in their path. However, the 2012 cruise showed much higher modulation in aerosol frequency than its 2011 counterpart. Whereas in 2011 large synoptic-scale aerosol events transported high concentrations of smoke into the Philippines over days, in 2012 measured aerosol events exhibited a much shorter-term variation, sometimes only 3–12 h. Strong monsoonal flow reversals were also experienced in 2012. Nucleation events in cleaner and polluted conditions, as well as in urban plumes, were observed. Perhaps most interestingly, several cases of squall lines preceding major aerosol events were observed, as opposed to 2011 observations where these lines largely scavenged aerosol particles from the marine boundary layer. Combined, these observations indicate pockets of high and low particle counts that are not uncommon in the region. These perturbations are difficult to observe by satellite and very difficult to model. Indeed, the Navy Aerosol Analysis and Prediction System (NAAPS) simulations captured longer period aerosol events quite well but largely failed to capture the timing of high-frequency phenomena. Ultimately, the research findings of these cruises demonstrate the real world challenges of satellite-based missions, significant aerosol life cycle questions such as those the future Aerosol/Clouds/Ecosystems (ACE) will investigate, and the importance of small-scale phenomena such as sea breezes, squall lines, and nucleation events embedded within SWM patterns in dominating aerosol life cycle and potential relationships to clouds
Climatology of surface meteorology, surface fluxes, cloud fraction, and radiative forcing over the southeast Pacific from buoy observations
Author Posting. © American Meteorological Society, 2009. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 22 (2009): 5527–5540, doi:10.1175/2009JCLI2961.1.A 5-yr climatology of the meteorology, including boundary layer cloudiness, for the southeast Pacific region is presented using observations from a buoy located at 20°S, 85°W. The sea surface temperature and surface air temperature exhibit a sinusoidal seasonal cycle that is negatively correlated with surface pressure. The relative humidity, wind speed, and wind direction show little seasonal variability. But the advection of cold and dry air from the southeast varies seasonally and is highly correlated with the latent heat flux variations. A simple model was used to estimate the monthly cloud fraction using the observed surface downwelling longwave radiative flux and surface meteorological parameters. The annual cycle of cloud fraction is highly correlated to that of S. A. Klein: lower-tropospheric stability parameter (0.87), latent heat flux (−0.59), and temperature and moisture advection (0.60). The derived cloud fraction compares poorly with the International Satellite Cloud Climatology Project (ISCCP)-derived low-cloud cover but compares well (0.86 correlation) with ISCCP low- plus middle-cloud cover. The monthly averaged diurnal variations in cloud fraction show marked seasonal variability in the amplitude and temporal structure. The mean annual cloud fraction is lower than the mean annual nighttime cloud fraction by about 9%. Annual and diurnal cycles of surface longwave and shortwave cloud radiative forcing were also estimated. The longwave cloud radiative forcing is about 45 W m−2 year-round, but, because of highly negative shortwave cloud radiative forcing, the net cloud radiative forcing is always negative with an annual mean of −50 W m−2.This research was supported by the Climate Prediction
Program for the Americas (CPPA) of NOAA’s
Climate Program Office. The Stratus Ocean Reference
Station at 20°S, 85°W is supported by NOAA’s Climate
Observation Program
Aerosol Meteorology of the Maritime Continent for the 2012 7SEAS Southwest Monsoon Intensive Study - Part 2: Philippine Receptor Observations of Fine-Scale Aerosol Behavior
The largest 7 Southeast Asian Studies (7SEAS) operations period within the Maritime Continent (MC) occurred in the August–September 2012 biomass burning season. Data included were observations aboard the M/Y Vasco, dispatched to the Palawan Archipelago and Sulu Sea of the Philippines for September 2012. At these locations, the Vasco observed MC smoke and pollution entering the southwest monsoon (SWM) monsoonal trough. Here we describe the research cruise findings and the finer-scale aerosol meteorology of this convectively active region. This 2012 cruise complemented a 2-week cruise in 2011 and was generally consistent with previous findings in terms of how smoke emission and transport related to monsoonal flows, tropical cyclones (TC), and the covariance between smoke transport events and the atmosphere’s thermodynamic structure. Biomass burning plumes were usually mixed with significant amounts of anthropogenic pollution. Also key to aerosol behavior were squall lines and cold pools propagating across the South China Sea (SCS) and scavenging aerosol particles in their path. However, the 2012 cruise showed much higher modulation in aerosol frequency than its 2011 counterpart. Whereas in 2011 large synoptic-scale aerosol events transported high concentrations of smoke into the Philippines over days, in 2012 measured aerosol events exhibited a much shorter-term variation, sometimes only 3–12 h. Strong monsoonal flow reversals were also experienced in 2012. Nucleation events in cleaner and polluted conditions, as well as in urban plumes, were observed. Perhaps most interestingly, several cases of squall lines preceding major aerosol events were observed, as opposed to 2011 observations where these lines largely scavenged aerosol particles from the marine boundary layer. Combined, these observations indicate pockets of high and low particle counts that are not uncommon in the region. These perturbations are difficult to observe by satellite and very difficult to model. Indeed, the Navy Aerosol Analysis and Prediction System (NAAPS) simulations captured longer period aerosol events quite well but largely failed to capture the timing of high-frequency phenomena. Ultimately, the research findings of these cruises demonstrate the real world challenges of satellite-based missions, significant aerosol life cycle questions such as those the future Aerosol/Clouds/Ecosystems (ACE) will investigate, and the importance of small-scale phenomena such as sea breezes, squall lines, and nucleation events embedded within SWM patterns in dominating aerosol life cycle and potential relationships to clouds
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Clouds, Aerosols, and Precipitation in the Marine Boundary Layer: An Arm Mobile Facility Deployment
The Clouds, Aerosol, and Precipitation in the Marine Boundary Layer (CAP-MBL) deployment at Graciosa Island in the Azores generated a 21-month (April 2009–December 2010) comprehensive dataset documenting clouds, aerosols, and precipitation using the Atmospheric Radiation Measurement Program (ARM) Mobile Facility (AMF). The scientific aim of the deployment is to gain improved understanding of the interactions of clouds, aerosols, and precipitation in the marine boundary layer.
Graciosa Island straddles the boundary between the subtropics and midlatitudes in the northeast Atlantic Ocean and consequently experiences a great diversity of meteorological and cloudiness conditions. Low clouds are the dominant cloud type, with stratocumulus and cumulus occurring regularly. Approximately half of all clouds contained precipitation detectable as radar echoes below the cloud base. Radar and satellite observations show that clouds with tops from 1 to 11 km contribute more or less equally to surface-measured precipitation at Graciosa. A wide range of aerosol conditions was sampled during the deployment consistent with the diversity of sources as indicated by back-trajectory analysis. Preliminary findings suggest important two-way interactions between aerosols and clouds at Graciosa, with aerosols affecting light precipitation and cloud radiative properties while being controlled in part by precipitation scavenging.
The data from Graciosa are being compared with short-range forecasts made with a variety of models. A pilot analysis with two climate and two weather forecast models shows that they reproduce the observed time-varying vertical structure of lower-tropospheric cloud fairly well but the cloud-nucleating aerosol concentrations less well. The Graciosa site has been chosen to be a permanent fixed ARM site that became operational in October 2013.Keywords: Atmosphere-ocean interaction, Decadal variability, Spring season, La Nina, Meridional overturning circulation, Hadley circulationKeywords: Atmosphere-ocean interaction, Decadal variability, Spring season, La Nina, Meridional overturning circulation, Hadley circulatio
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Turbulence and Mass-Transports in Stratocumulus Clouds
Boundary layer (BL) stratocumulus clouds are an important factor in the earth\u27s radiation budget due to their high albedo and low cloud top heights. Continental BL stratocumulus clouds are closely coupled to the diurnal cycle and the turbulence in the BL affecting the surface energy and moisture budgets. In this study the turbulence and mass-transport structures in continental BL stratocumulus clouds are studied using data from the Atmospheric Radiation Measurements (ARM)\u27s Southern Great Plains (SGP) observing facility located at Lamont, Oklahoma. High temporal (4 sec) and spatial (45 m) resolution observations from a vertically pointing 35 GHz cloud Doppler radar were used to obtain the in-cloud vertical velocity probability density function (pdf) in the absence of precipitation size hydrometeors. A total of 70 hours of radar data were analyzed to report halfhourly statistics of vertical velocity variance, skewness, updraft fraction, downdraft and velocity binned mass-flux at five cloud depth normalized levels. The variance showed a general decrease with increase in height in the cloud layer while the skewness is weakly positive in the cloud layer and negative near cloud top. The updraft fraction decreases with height with the decrease mainly occurring in the upper half of the cloud layer. The downdraft fraction increases with decrease in height with the increase being almost linear. The velocity of eddies responsible for maximum mass-transport decreases from of 0.4 ms-1 near cloud base to 0.2 ms-1 near cloud top. The half-hour periods were then classified based on the surface buoyancy flux as stable or unstable and it was found that the variance near cloud top is higher during the stable periods as compared to the unstable periods. Classification was also made based on the cloud depth to BL depth ratio (CBR) being greater or less than 0.3. The variance profile was similar for the classification while the skewness was almost zero during periods with CBR less 0.3 and positive during periods with CBR greater than 0.3. A 14 hour period of stratocumulus cloud on March 25, 2005 was analyzed to study the diurnal changes in the turbulence structure and mass transports. The variance near cloud base during the day time when the BL turbulence is primarily due to surface buoyancy production was higher than during the nighttime when the BL turbulence is driven by radiative cooling near the cloud top. Output from a one dimensional radiative transfer model was analyzed to study the vertical structure of the radiative fluxes. A radiative velocity scale analogous to the surface convective velocity scale is proposed to assess the relative importance of radiative cooling near cloud top in generating turbulence compared with the surface buoyancy production. An attempt was also made to calculate the hourly liquid water flux by combining the high temporal resolution (20 sec) liquid water content estimates from the radar reflectivity and a microwave radiometer with the radar observed vertical velocity. The liquid water flux was found to peak at a level below the cloud top and show a divergence with height that was similar to that from model simulations