详细信息
id
4
标题
TOMS卫星臭氧及反射率逐日观测数据集(1987-1993)
描述
TOMS卫星臭氧及反射率逐日观测数据集(1987-1993)
资料集名称: TOMS卫星臭氧及反射率逐日观测数据集
责任者: 资料中心
资料集编号: DS066
索取号: C6066、C6067
索引名: toms
记录年代: 1987年—1993年
区域:
要素: 臭氧、反射率
编排: 统计报告
统计特征: 观测数据
详介:
观测次数、时间:
站数/层数、层次:
载体说明: CD-ROM光盘
数量: 2张
资料来源: NASA Langley Research Center
参考文献: TOMS Version 7 May 22, 1996
Gridded O3 Data: 1978-1993
TOMS Version 7 May 22, 1996
Gridded O3 Data: 1978-1993
INTRODUCTION

This 2 CD-ROM set contains the latest version (version 7) of ozone

data from the TOMS (Total Ozone Mapping Spectrometer) instrument

onboard the Nimbus 7 spacecraft. Data covering the entire Nimbus 7

TOMS lifetime, November 1, 1978 through May 6, 1993, are given

as daily files of gridded data, as zonal means, and as monthly

averages. Software is included to image the data.

For scientific investigators, a similar CD-ROM containing TOMS

surface reflectivity values is planned. A CD-ROM of version 7 data

from the Meteor 3 TOMS instrument (August 1991 - December 1994)

will be produced this summer.

HARDWARE REQUIREMENTS

For PC: The data on this CD-ROM are ASCII format and can be

accessed by most systems. The image display software requires

Microsoft Windows and a VGA or better graphics card that can

support at least 256 colors. For best performance, a 486 or faster

machine with a math co-processor is recommended.

For Mac: Because the software is designed for a multi-platform

environment, it has been written to the ISO 9660 Standard. All

filenames are given in the 8.3 format. For best performance, a 68030

or faster machine is recommended. Graphic support for at least 256

colors is recommended.

 

OVERVIEW OF THIS CD-ROM

The first CD-ROM, designated OPT_004A, contains daily and

monthly gridded data for the period November 1978 through 1987.

The second CD-ROM, designated OPT_004B, contains similar data

for 1988 through May 1993, along with daily and monthly zonal

means, TOMS "overpass" data for 371 individual ground locations,

and daily GIF images. The data are described in more detail in the

DATA FILES section. Each CD-ROM contains a DOCUMENT

subdirectory that has a full copy of the TOMS User's Guide in Adobe

Acrobat format. Each also contains a SOFTWARE subdirectory with

PC and MAC subdirectories containing platform-specific software to

image or view the data.

 

THE OZONE MEASUREMENT

The Nimbus 7 spacecraft was in a south-to-north, sun-synchronous

polar orbit so that it was always close to local noon/midnight below

the spacecraft. Thus, ozone measurements were taken for the entire

world every 24 hours. TOMS directly measures the ultraviolet

sunlight scattered by the Earth's atmosphere. Total column ozone is

inferred from the differential absorption of scattered sunlight in the

ultraviolet range. Ozone is calculated by taking the ratio of two

wavelengths (312 nm and 331 nm, for example), where one

wavelength is strongly absorbed by ozone while the other is absorbed

only weakly. The instrument has a 50 kilometer square field of view

at the sub-satellite point. TOMS collects 35 measurements every 8

seconds as it scans right to left producing approximately 200,000

ozone measurements daily. These individual measurements vary

typically between 100 and 650 Dobson Units (DU) and average about

300 DU. This is equivalent to a 3 mm (about a 10th of an inch) thick

layer of pure ozone gas at NTP conditions.

 

THE DATA FILES

Gridded Daily: The individual TOMS measurements have been

averaged into grid cells covering 1 degree of latitude by 1.25

degrees of longitude. The 180x288 ASCII data array contains data

from 90S to 90N, from 180W to 180E. Each ozone value is a 3

digit integer (see sample). LECT is the local equator crossing time.

Both CDs example: .n7t

sample data:

Day: 281 Oct 8, 1987 Production V70 NIMBUS-7/TOMS OZONE Asc LECT: 11:35 AM

Longitudes: 288 bins centered on 179.375 W to 179.375 E (1.25 degree steps)

Latitudes : 180 bins centered on 89.5 S to 89.5 N (1.00 degree steps)

144144144144144144144144144144144144144144144144144144144144144144144144145

145145145149149149149161161161161149149149149149149149149149149149149149149

149149149149149149149149149149142142142142143143143143143143143143143143143

143140140140140140140140140140140140140140140140140140140140140140140140140

140140140140140140140140140140140140140140140140140140140140148148148148148

148148148148148148148148148148148148148148148148148148148148148148148148148

148148147147147147147147147147145145145145143143143143143143143143143143143

143143143143143143143143143143143143143143143143143143143143143143143143143

143143143143143143143143153153153153153153153153153153153153153153153153161

161161161160160160160160160160160160160160160146146146146144144144144144144

144144144144144144144144144144144144144144144144144144144144144144144144144

144144144144144144144144144144144144144 lat = -89.5

Gridded Monthly Average: Data in the same format as the gridded

daily, but averaged for each month. For each grid cell at least 20

days of data must be good for the average to be computed.

Both CDs example: .n7t

GIF Image: Each day of data has a corresponding GIF image. Each

image is 640x480 pixels (full screen in standard VGA) at 256

colors. North polar, south polar, and Aitoff projections are

shown.

2nd CD only example: .gif

Overpass Data: These files contain "overpass" data, the best match

single TOMS observation each day, for 371 ground locations

worldwide. (Dobson and other science sites, along with major

cities) See README file in for list of sites.

2nd CD only example: .n7t

Zonal Means: Daily and monthly averaged data in 5? latitude zones.

At least 75% of possible data must be present for the mean to be

given.

2nd CD only example: .n7t

example: _79.n7t

PROBLEMS WITH THE DATA

Polar Night: Because TOMS measures ozone using scattered

sunlight, it is not possible to measure ozone when there is no sun (in

the polar regions in winter). Consequently, maps of the Antarctic

ozone hole for August and September, for example, will always have

areas of missing data due to polar night.

Missing Data: During 1978/1979 the TOMS instrument was turned

off periodically to conserve power, including a 5 day period

(6/14-6/18) in June 1979. On many days, data were lost due to

missing orbits or other problems.

Edge Effects: At the transition between good and flagged or missing

data, an "edge effect" will appear, consisting of a few pixels of

apparently low ozone values. These are artifacts generated when the

original data were interpolated to produce the stored image data. A

second type of edge effect will be noticed in the polar plots consisting

of apparent discontinuities in the ozone field. Since TOMS takes 24

hours to map the entire Earth, near the dateline the ozone

measurements have been taken almost 24 hours apart. If the ozone is

changing with time, this will produce the observed discontinuity.

High Terrain: The ozone reported is total column ozone to the

ground. Over high mountains (the Himalayas, the Andes) low ozone

will be noticed relative to surrounding low terrain. This is not an

error.

 

SOFTWARE DESCRIPTION

1. LVIEW and JPEGVIEW

Lview 3.1 is a freeware imaging program for Windows which can

easily view GIF and JPG images.

JpegView is a commonly used image viewer for the Macintosh. It

can read JPG, GIF and other image formats.

2. THE VISUANALYZE LITE PROGRAM

VisuAnalyze Lite is designed to provide the user with a means of

viewing the daily ozone data. Once loaded, the program will display

a window consisting of a pull down menu and three boxes: one each

for the image, the data table and the site information selected by the

cursor.

The menu allows you to control the viewing process and has a

number of controls over the screen image. North Orthographic,

South Orthographic, and Hammer-Aitoff projections are supported.

An overlay provides grid and continental maps for easy reference.

Palette permits the user to select between different color patterns to

aid in image analysis. VisuAnalyze Lite allows the opening of as

many windows as memory permits. There are minor differences

between the MAC and PC versions.

The included version is limited to viewing TOMS data; for more

information on the program or for information on obtaining the

unlimited version contact:

Bharat Thacker

Research and Professional Services (RPS)

5711 Sarvis Avenue, Suite 510

Riverdale, Maryland 20737 USA

(301) 699-7771 or (313) 278-7719

 

 

 

DIRECTORY STRUCTURE

CDROM #1 - OPT_004A

root

(TOMS User's guide)

(Source Code Templates)

 

(MAC Acrobat reader)

(MAC .GIF viewer)

(MAC imaging software)

 

(PC Acrobat reader)

(PC .GIF viewer)

(PC imaging software)

(Month average grid files)

(Daily grid files)

 

CDROM #2 - OPT_004B

root

(TOMS User's guide)

(identical to 1st CD)

 

 

(Daily GIF images)

(by location number - see README file)

(Month average grid files)

(Daily grid files)

(Monthly average zonal means)

(Daily average zonal means)

 

DOCUMENTATION

There are README files on the CD-ROM for all of the software

under the appropriate directory. A complete copy of the TOMS

User's Guide is on the CD-ROM in PDF Format. Adobe Acrobat

readers are included in the subdirectories

and .

Free Adobe Acrobat readers for other platforms can be found on the

Adobe homepage at: http://www.adobe.com

 

INTERNET SERVICES

NASA/Goddard Space Flight Center's Laboratory for Atmospheres

has a Web Site devoted to Atmospheric Science. This site contains

ozone related information including aircraft missions, spacecraft,

tropospheric data, atmospheric modeling, and more. The URL

address of this site is:

http://hyperion.gsfc.nasa.gov

 

News about the TOMS data, the upcoming Earth Probe and ADEOS

TOMS missions, and any software updates will appear on the TOMS

homepage. For Internet access to the TOMS Home Page use URL

address:

http://jwocky.gsfc.nasa.gov

Direct data access is available via an anonymous FTP account:

ftp jwocky.gsfc.nasa.gov.

logon: anonymous

password: your e-mail address

cd pub/nimbus7

 

 

CONTACTS

Dr. Richard McPeters (science)

NASA Goddard Space Flight Center, Code 916

Greenbelt, Maryland 20771 USA

mcpeters@wrabbit.gsfc.nasa.gov

(301) 286-3832 (301) 286-1754 (fax)

Eric Beach (general)

Hughes STX

7701 Greenbelt Road, M/S 301H

Greenbelt, Maryland 20771 USA

beach@qhearts.gsfc.nasa.gov

(301) 286-4526 (301) 286-1754 (fax)l TOMS卫星臭氧及反射率逐日观测数据集(1987-1993)
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