GIS for Atmospheric Sciences and Hydrology

By David R. Maidment

University of Texas at Austin

National Center for Atmospheric Research, 6 July 2005

GIS for Atmospheric Science and Hydrology

• Space-time data models

• Hydrologic observations data

• Weather and climate data

• Common data model

Atmospheric science – hydrology

• Weather and climate fields are the drivers – continuous in space and time across the nation

• Hydrologic flows in watersheds are the reactors – behaving according to watershed location and characteristics

Issues

• Atmospheric science describes a fluid domain continuous in space and time, globally connected

• The earth’s surface is a static, highly spatially varied domain whose water properties vary continuously in time, where water is concentrated in flow paths (streams and rivers)

Issues

• Atmospheric science data are spatially extensive (e.g. North America), involve many variables, are “thin” in time (one day, one forecast period, one month), and use UTC time coordinates

• Hydrologic data are spatially localized (e.g. my watershed), involve few variables (precipitation, evaporation, runoff), are “deep” in time (many decades), and use local time coordinates

This space-time recompositing problem Is not trivial!

Issues

• Atmospheric science data are stored in vary large binary files with specialized formats (Grib, netCDF, XMRG, ….) whose georeferencing may not be strong

• Hydrologic data are stored in tables in GIS and relational databases, and accessed using GIS spatial and SQL queries

How do we connect these very different data worlds?

Space, L

Time, T

Variables, V

D

Data Cube

Continuous Space-Time Data Model -- NetCDF

Space, L

Time, T

Variables, V

D

Coordinate dimensions

{X}

Variable dimensions{Y}

Space, FeatureID

Time, TSDateTime

Variables, TSTypeID

TSValue

Discrete Space-Time Data Model-- Arc Hydro

Geospatial Time Series

Value

Time

Shape

Time SeriesProperties

(Type)A Value-Time array

A time series that knows what geographic feature it describes and what type of time series it is

GIS for Atmospheric Science and Hydrology

• Space-time data models

• Hydrologic observations data

• Weather and climate data

• Common data model

Data Model for Hydrologic Observations

Relationships

USGS National Water Information System

Access is rapid enough that it is as if NWIS is a local disk on your computer

CUAHSI Data Portal

CUAHSI Data Portal

Plot from the Hydrology Data PortalProduced using a CUAHSI Hydrology Web Service: getDailyStreamflowChart

Applications and Services

Web ServicesLibrary

Web application: Data PortalYour application• Excel, ArcGIS, Matlab• Fortran, C/C++, Visual Basic• Hydrologic model• …………….

Your operating system• Windows, Unix, Linux, Mac

Internet

GIS for Atmospheric Science and Hydrology

• Space-time data models

• Hydrologic observations data

• Weather and climate data

• Common data model

http://wwwt.emc.ncep.noaa.gov/mmb/rreanl/

A retrospective study of weather and climate made by the National Centers for Environmental Prediction’s (NCEP)

numerical weather prediction model and observations from 1979 to 2003 to make 3 hour forecasts. 3 hour, daily and

monthly data are available on a 32 km grid over North America.

Using IDV and THREDDS to access NARR

NARR.xml

Get NARR.xml from NARR home page

NARR at Asheville, NC

IDV in Austin, TX

Precipitable Water and Specific Humidity over Gulf

0.005 0.020 Specific humidity (kg/kg)

Alti

tude

Precipitable Water and Specific Humidity over Texas

0.005 0.020 Specific humidity (kg/kg)

Alti

tude

Precipitation

July 2003, 1800Z

Surface evaporation

July 2003, 1800Z

GIS for Atmospheric Science and Hydrology

• Space-time data models

• Hydrologic observations data

• Weather and climate data

• Common data model

NetCDF-Java version 2.2 Common Data Model

John Caron

Unidata/UCAR

Dec 10, 2004

NetcdfDataset

Application

Scientific Datatypes

Grid Station Image

NetCDF-Java version 2.2 architecture

ADDEOpenDAPTHREDDS

Catalog.xml NetCDF-3

HDF5

I/O service provider

GRIB

GININIDS

NetcdfFile

NetCDF-4

…NexradDMSP

File Format#N

File Format#2

File Format#1

CDM

Visualization&Analysis

Goal: N + M instead of N * M things on your TODO List

NetCDF file

Data Server

Web Service

ArcGIS ModelBuilder Application for Automated Water Balancing

Conclusions

• Data access through web services can mask the variations in data structure between relational databases and data file systems

• We need a “Common, common” data model to better integrate GIS and weather and climate information

• We need tools for space-time recompositing of weather and climate information to make it suitable for hydrology