Siri Jodha Singh Khalsa

Remote sensing and GIS technology in the Global Land Ice Measurements from Space (GLIMS) Project

Global Land Ice Measurements from Space (GLIMS) is an international consortium established to acquire satellite images of the worlds glaciers, analyze them for glacier extent and changes, and to assess these change data in terms of forcings. The consortium is organized into a system of Regional Centers, each of which is responsible for glaciers in their region of expertise. Specialized needs for mapping glaciers in a distributed analysis environment require considerable work developing software tools: terrain classification emphasizing snow, ice, water, and admixtures of ice with rock debris; change detection and analysis; visualization of images and derived data; interpretation and archival of derived data; and analysis to ensure consistency of results from different Regional Centers. A global glacier database has been designed and implemented at the National Snow and Ice Data Center (Boulder, CO); parameters have been expanded from those of the World Glacier Inventory (WGI), and the database has been structured to be compatible with (and to incorporate) WGI data. The project as a whole was originated, and has been coordinated by, the US Geological Survey (Flagstaff, AZ), which has also led the development of an interactive tool for automated analysis and manual editing of glacier images and derived data (GLIMSView). This article addresses remote sensing and Geographic Information Science techniques developed within the framework of GLIMS in order to fulfill the goals of this distributed project. Sample applications illustrating the developed techniques are also shown.

Challenges and recommendations in mapping of glacier parameters from space: results of the 2008 Global Land Ice Measurements from Space (GLIMS) workshop, Boulder, Colorado, USA

Abstract On 16–18 June 2008 the US National Snow and Ice Data Center held a GLIMS workshop in Boulder, CO, USA, focusing on formulating procedures and best practices for operational glacier mapping using satellite imagery. Despite the progress made in recent years, there still remain many cases where automatic delineation of glacier boundaries in satellite imagery is difficult, error prone or time-consuming. This workshop identified six themes for consideration by focus groups: (1) mapping clean ice and lakes; (2) mapping ice divides; (3) mapping debris-covered glaciers; (4) assessing changes in glacier area and elevation through comparisons with older data; (5) digital elevation model (DEM) generation from satellite stereo pairs; and (6) accuracy and error analysis. Talks presented examples and work in progress for each of these topics, and focus groups worked on compiling a summary of available algorithms and procedures to address and avoid identified hurdles. Special emphasis was given to establishing standard protocols for glacier delineation and analysis, creating illustrated tutorials and providing source code for available methods. This paper summarizes the major results of the 2008 GLIMS workshop, with an emphasis on definitions, methods and recommendations for satellite data processing. While the list of proposed methods and recommendations is not comprehensive and is still a work in progress, our goal here is to provide a starting point for the GLIMS regional centers as well as for the wider glaciological community in terms of documentation on possible pitfalls along with potential solutions.

Air‐sea fluxes and surface layer turbulence around a sea surface temperature front

The observed effects of sharp changes in sea surface temperature (SST) on the air-sea fluxes, surface roughness, and the turbulence structure in the surface layer and the marine atmospheric boundary layer are discussed. In situ flux and turbulence observations were carried out from three aircraft and two ships within the FASINEX framework. Three other aircraft used remote sensors to measure waves, microwave backscatter, and lidar signatures of cloud tops. Descriptions of the techniques, intercomparison of aircraft and ship flux data, and use of different methods for analyzing the fluxes from the aircraft data are described. Changing synoptic weather on three successive days yielded cases of wind direction both approximately parallel and perpendicular to a surface temperature front. For the wind perpendicular to the front, wind over both cold-to-warm and warm-to-cold surface temperatures occurred. Model results consistent with the observations suggest that an internal boundary layer forms at the SST.

A Climatology of the Water Vapor Band Brightness Temperatures from NOAA Operational Satellites

Abstract Measurements of brightness temperature from the water vapor band channels of the National Oceanic and Atmospheric Administration polar satellites from 1981 through 1988 are analyzed. Only clear and cloud-cleared measurements from the operational sounding product are used to produce averages for bins of 2.5° latitude by 2.5° longitude and 5 days. The standard deviations of random errors for these bins are estimated. A unique feature of this dataset is its ability to identify the dry regions in the middle and upper troposphere with unprecedented detail. Results agree with the known climatology in the tropics.

Rapid ASTER Imaging Facilitates Timely Assessment of Glacier Hazards and Disasters

Glacier- and permafrost-related hazards increasingly threaten human lives, settlements, and infrastructure in high-mountain regions. Present atmospheric warming particularly affects terrestrial systems where surface and sub-surface ice are involved. Changes in glacier and permafrost equilibrium are shifting beyond historical knowledge. Human settlement and activities are extending toward danger zones in the cryospheric system. A number of recent glacier hazards and disasters underscore these trends. Difficult site access and the need for fast data acquisition make satellite remote sensing of crucial importance in high-mountain hazard management and disaster mapping.

Updraft and Downdraft Events in the Atmospheric Boundary Layer Over the Equatorial Pacific Ocean

Abstract Conditional sampling has been applied to aircraft turbulence measurements in order to study updrafts and downdrafts over the central equatorial Pacific Ocean. Average event size, number density and proportion of time series occupied are obtained for the drafts, along with conditional averages of horizontal momentum, moisture and virtual temperature and the draft contributions to the total fluxes. It is found that updrafts are usually cool/moist and warm/moist while downdrafts are most often warm/dry. Convective mass flux parameterizations of the sensible and latent heat flux are tested. Results consistent with previous workers are obtained when the flux production is mainly by updrafts. However, when downdrafts dominate, they must be taken into account explicitly in order for the parameterization to be accurate.

Space-based mapping of glacier changes using ASTER and GIS tools

We describe an investigation that combines space-based observations of glacier parameters with historical glaciological data derived by traditional means to predict changes in ice extent and volume for the Ak-shirak Range in the interior Tien Shan of Central Asia. A variety of geographic information systems and photogrammetric tools are used to extract glacier outlines, derive of a digital elevation model, and compute area versus elevation distribution functions from data acquired by the Advanced Spaceborne Thermal Emission and Reflection radiometer. These products are then used in a glaciological methodology that can predict the response of glacier systems to changes in local climate.

Representing scientific data sets in KML: Methods and challenges

Virtual Globes such as Google Earth and NASA World Wind permit users to explore rich imagery and the topography of the Earth. While other online services such as map servers provide ways to view, query, and download geographic information, the public has become captivated with the ability to view the Earths features virtually. The National Snow and Ice Data Center began to display scientific data on Virtual Globes in 2006. The work continues to evolve with the production of high-quality Keyhole Markup Language (KML) representations of scientific data and an assortment of technical experiments. KML files are interoperable with many Virtual Globe or mapping software packages. This paper discusses the science benefits of Virtual Globes, summarizes KML creation methods, and introduces a guide for selecting tools and methods for authoring KML for use with scientific data sets.

Conditional Sampling of Updrafts and Downdrafts in the Marine Atmospheric Boundary Layer

Abstract The properties of updrafts and downdrafts in the lower third of the marine atmospheric boundary layer (MABL) over the central Pacific Ocean are investigated using a conditional sampling technique. When the drafts are classified according to their heat and moisture content, the properties of the major classes (moist updrafts and dry downdrafts) are in agreement with a parcel displacement model of vertical mixing. The minor class events appear to be the result of the reversal of motion of the major class events. Drafts that consume turbulent kinetic energy (TKE), although small in number in the lower third of the MABL, have spatial scales comparable with drafts that produce TKE. At the lowest level, the area occupied by positively buoyant downdraft exceeds the area occupied by negatively buoyant updrafts by a factor of 2. Updrafts and downdrafts produce a large fraction of the total fluxes of heat moisture and momentum, increasing from 75% at 0.07zi to 85% at 0.32zi. Of the draft contribution to th...

Convective Elements in the Marine Atmospheric Boundary Layer. Part I: Conditional Sampling Statistics

Abstract The properties of updrafts and downdrafts through the entire depth of the marine atmospheric boundary layer are investigated using conditional sampling based on an indicator function derived from the vertical velocity time series. Statistics on event size, number density and area occupied are obtained, along with conditional averages of the meteorological variables and percent contributions to the fluxes by updrafts, downdrafts and the environment. A single profile is obtained for convective mass flux based on conditional averaging of updrafts and downdrafts applicable to the fluxes of latent and sensible heat and momentum.