Jungle Research Group
at the Atmospheric Sciences Research Center

HVAMS

For the last fifty years it has often been argued that studies of the lower atmosphere should concentrate on understanding the most elementary situations; we are to attack the more difficult problems later. Following this line, many projects continue to be set in unforested places with little topographic variation. Studies of meteorology in "complex terrain" have focused on extremely mountainous regions, such as the Rockies or the Alps. Between these extremes is a large expanse of regions with moderately complex topography and more complicated land surfaces, places where people live and weather and pollution forecasts must be made. With the rapid increase in quality and quantity of remote sensing imagery, many are proposing techniques to reduce surface boundary conditions to counting tiles in the appropriate mosaic. How will these approaches be tested? In this project, we turn deliberately to study this intermediate ground. We believe that many of the problems associated with the lack of horizontal homogeneity can be offset by the appearance of regular local winds, which make it easier to form useful composites.

This investigation of the Hudson Valley, New York intends to examine how local topography and land use patterns affect boundary layer dynamics under predominantly fair-weather conditions. 

We believe that valley-induced circulations induce a diurnal regularity to boundary layer structure that allows patterns to be detected efficiently.  That is, we have a better idea when to look and what to look for.  Thus, while our primary focus is on the description of flows in the Hudson Valley, results of more general interest to boundary layer meteorology are likely to emerge from this work.

The Hudson Valley

The Hudson/Champlain Valley (the "Valley") system extends NNE more than 500 km from New York City to the Canadian border.  Just above Albany, NY, the Mohawk River flows into the Hudson. Valley sidewalls range from less than 100 m at White Plains to over 1000 m near the Catskills, but generally rise 200 - 300 m above the river.  For most of its length the valley is about 20 - 30 km wide, but it narrows to less than 5 km near West Point.

The project has been executed in stages, starting with consolidation of and analysis of diverse existing meteorological and land use data sets.  Then, long-term (2-year) observations were initiated, and these set the stage and provide context for a six-week intensive observation period. During the intensive observations, a fine-scale network of turbulence observations, enhanced remote sensing capability and aircraft measurements allowed us to study the physical mechanisms responsible for surface-atmosphere exchanges in the valley.  Following the intensive observations, we proposed a full analysis and modeling program, one that includes interaction with colleagues at UAlbany and at two outside institutions. The stages of the plan are:

1. Preliminary data analysis: Integration of existing surface observation networks and historical datasets. Within and adjacent to the valley, several different agencies operate meteorological surface observation networks (Fig. 8). The National Weather Service (NWS) and Federal Aviation Administration (FAA) operate several Automated Surface Observing System (ASOS) stations that measure temperature, humidity, pressure, wind direction, wind speed, sky condition, and precipitation.  Archived 1-minute resolution ASOS data is available from the National Climatic Data Center (NCDC).  The Albany NWS Forecast Office (Albany WFO) oversees a network of Cooperative Observer (COOP) and Supplemental Weather Information Network (SWIN) stations regionally that report daily maximum and minimum temperatures and precipitation. The New York State Department of Environmental Conservation (NYSDEC) manages a few field stations that provide hourly observations of SO2, CO, O3, and PM10, and meteorological data such as temperature, humidity, and wind speed and direction. The New York City Department of Environmental Protection (NYCDEP) operates over twenty stations in the Catskills, including hourly-averaged 5-min measurements of temperature, humidity, winds, precipitation, and insolation.

2. Long-term Deployment 

a. Surface meteorological observations. The currently expanding New York State Department of Transportation (NYSDOT) weather station network, standard ASOS measurements at Albany Airport, and the NWS Cooperative observers are the core of our long-term deployment. Five new automated weather stations (Campbell Scientific, Inc.) were equipped to observe temperature, humidity, wind vector, barometric pressure, soil temperature, net and solar radiation to fill in gaps and to provide more frequent reports.

b. "Anchor" observation tower. This UASUNY station is located at Grieg Farm, the nexus of the field deployment scheme. It includes measurements of radiation, turbulent heat water vapor, and CO2 fluxes, soil temperature, as well as CO2 and ozone concentrations. This anchor station, largely instrumented with equipment on hand at ASRC, provides a context for the data obtained by the more comprehensive network of instrument platforms that were deployed during the intensive field campaign.

c. Long-term observations and remote sensing plan. We plan to merge data from the NOAA profiler, regional ASOS stations and GOES images to build a project data resource. As part of cost sharing, UASUNY has purchased a Remtech PA-0 acoustic sounder, which was deployed near one of the automatic weather stations for several months each year. An archive of relevant LANDSAT images and fine-scale GIS datasets were compiled to facilitate our studies of landscape—land use and topography.  

a. Surface network. Nine Integrated Surface Flux Facility (ISFF) platforms were located at sites featuring different land-use types and local exposure conditions, to capture heterogeneities in radiative and surface fluxes, keys to identifying local forcings.  Four sites (including the anchor station) will make measurements of O3 concentrations, as well as employ microbarometers to estimate cross-valley and up valley —p. We aim to use ozone as a tracer not only of stable BL breakdowns, but also as a way to track daytime advection from more urban regions. Fast response (1 Hz) data sequences will be examined to identify preferred regions for nocturnal mixing events. Once stations are operational, they will be checked daily for quality control. Data will be archived at 1 min or 1 s intervals, depending on feasible data transfer rates.

b. Aircraft observations. The flux measurements on the University of Wyoming King Air (UWKA), plus time series of moisture, temperature, and trace gas profiles are essential components for determining the link between land and surface properties, surface fluxes, long-range transport, mesoscale variability in the boundary layer. The UWKA will make the high spatial and temporal resolution measurements of meteorological variables within and above the valley that are necessary to capture the small scale perturbations in the temperature and pressure fields responsible for valley-induced circulations. The aircraft is equipped with rapid response instruments that have proven to yield accurate flux estimates of momentum, sensible and latent heat, and trace gases such as O3 and CO2.

UWKA flights: Two types of flights of 3-4 hour duration (at a speed of 70 m s-1) will be flown during the intensive observation period. The first flight will begin at 0600 LT with a second flight scheduled for around 1500 LT. Both flight plans will include measurement overlap with other goals. The early morning flight will attempt to observe the latter stages of the NBL and the CBL rapid growth phase, while the afternoon flight will include observations relevant to CBL structure and subsequent decay. Flight tracks will be along- and cross-valley, concentrated over locations containing flux towers, and flown as vertical stacks, with the highest cross-valley tracks extended (to 100 km) to observe elevated mixed layers over the Catskill Mountains.

c. Balloon based soundings. TAOS (Tethered Atmospheric Observation System, NCAR) will be employed to observe sequences of environmental stability, moisture, temperature, and wind profiles in the lowest 300 m of the atmosphere.

National Weather Service personnel at the Albany Weather Forecast Office will launch additional high resolution (5m) soundings (up to every 3 hours), including a number of ozone sondes, to determine profiles of temperature, humidity, winds, and ozone concentration in the remnant CBL at night.

d. Remote sensing plan. MIPS (K. Knupp, U. of Alabama, Huntsville) will be deployed at a central site south of the surface station array on or near the river. This unit consists of a 915MHz Doppler profiler, a Doppler sodar equipped with RASS, a Vaisala CT-25K ceilometer, a 12-channel microwave profiler radiometer, and a surface station. The MIPS principal function will be to obtain continuous high vertical resolution observations of convective boundary layer growth, evolution, and decay, and to observe the formation and subsequent decay of the nocturnal boundary layer and NBLJ structure.