|
|
|
1.2250 kgm-3
0.076474 lbm/ft3
1.2250 g/liter
0.001225 g/cm3
|
kilograms per cubic meter
pounds-mass per cubic foot
grams per liter
grams per cubic centimeter
|
|
Back to the Table of Contents
| Characteristics of gases in the air near the ground. Molecular weights
are in g/mole. The volume fraction indicates the relative contribution to
air in the earth's lower atmosphere. EPA is the USA Environmental Protection
Agency. |
|
Symbol
|
Name
|
Molecular Weight
|
Volume Fraction%
|
|
| Constant Gases |
|
N2
O2
Ar
Ne
He
H2
Xe
|
Nitrogen
Oxygen
Argon
Neon
Helium
Hydrogen
Xenon
|
28.01
32.00
39.95
20.18
4.00
2.02
131.30
|
78.08
20.95
0.93
0.0018
0.0005
0.00005
0.000009
|
|
| Variable Gases |
|
|
Water vapor
Carbon dioxide
Methane
Nitrous oxide
|
|
0 to 4
0.035
0.00017
0.00003
|
|
| EPA Air Quality Standards |
|
|
Carbon monoxide
Sulfur dioxide
Ozone
Nitrogen dioxide
|
|
0.0035
0.000014
0.000012
0.000005
|
|
| Mean Condition for Air |
|
|
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| VARIABLE |
USEFULNESS |
| Maximum
temperature |
Highly
correlated with ozone and ozone formation |
| Morning
wind speed |
Associated
with dispersion and dilution of ozone precursor pollutants |
| Afternoon
wind speed |
Associated
with transport of ozone |
| Cloud cover |
Controls
solar radiation, which influences photochemistry |
| Relative
humidity |
Surrogate
for cloud cover |
| 500-mb
height |
Indicator
of the synoptic-scale weather pattern |
| 850-mb
temperature |
Surrogate
for vertical mixing |
| Pressure
gradients |
Causes
winds and ventilation |
| Day of
week |
Emissions
differences |
| Morning
NOx concentration |
Ozone precursor
levels |
| Previous
day's peak ozone |
Persistence,
carry-over |
| Aloft wind
speed and direction |
Transport
from upwind region |
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| Droplet or Nuclei |
Average Diameter
(micrometers) |
| Typical CCN |
0.2 |
Typical Cloud Droplet |
20 |
Large Cloud Droplet |
100 |
Typical Raindrop
| 2000
|
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| Values are for over a flat surface
of liquid water. r and q values are for sea level. e
and pv values are for any pressure. T
is temperature, Td is dew-point temperature,
e is vapor pressure, r is mixing ratio, q is specific
humidity, pv is absolute humidity, and subscript
s denotes a saturation value. |
|
|
|
or
|
|
|
|
(oC)
|
(kPa)
|
(g/kg)
|
(g/kg)
|
(kg/m3)
|
|
-20
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
44
46
48
50
|
0.127
0.150
0.177
0.209
0.245
0.287
0.335
0.391
0.455
0.528
0.611
0.706
0.814
0.937
1.076
1.233
1.410
1.610
1.835
2.088
2.371
2.688
3.042
3.437
3.878
4.367
4.911
5.514
6.182
6.921
7.736
8.636
9.627
10.717
11.914
13.228
|
0.78
0.92
1.09
1.28
1.51
1.77
2.07
2.41
2.80
3.26
3.77
4.37
5.04
5.80
6.68
7.66
8.78
10.05
11.48
13.09
14.91
16.95
19.26
21.85
24.76
28.02
31.69
35.81
40.43
45.61
51.43
57.97
65.32
73.59
82.91
93.42
|
0.78
0.92
1.09
1.28
1.51
1.76
2.06
2.40
2.80
3.25
3.76
4.35
5.01
5.77
6.63
7.60
8.70
9.95
11.35
12.92
14.69
16.67
18.89
21.38
24.16
27.26
30.72
34.57
38.86
43.62
48.91
54.79
61.31
68.54
76.56
85.44
|
0.00109
0.00128
0.00150
0.00175
0.00204
0.00237
0.00275
0.00318
0.00367
0.00422
0.00485
0.00557
0.00637
0.00728
0.00830
0.00945
0.01073
0.01217
0.01377
0.01556
0.01755
0.01976
0.02222
0.02494
0.02794
0.03127
0.03493
0.03896
0.04340
0.04827
0.05362
0.05947
0.06588
0.07287
0.08051
0.08884
|
|
Back to the Table of Contents
|
101.325 kPa
1013.25 hPa
101,325. Pa
101,325. Nm-2
101,325 kgmm-1s-2
1.033227 kgfcm-2
1013.25 mb
1.01325 bar
14.69595 psi
2116.22 psf
1.033227 atm
760 Torr
|
kiloPascals
hectoPascals
Pascals
Newtons per square meter
kg-mass per meter per s2
kg-force per square cm
millibars
bars
pounds-force / square inch
pounds-force / square foot
atmosphere
Torr
|
|
Back to the Table of Contents
Universal
Time Convention
(UTC) | Eastern
Standard Time (EST) | Central
Standard Time (CST) | Mountain
Standard Time (MST) | Pacific
Standard Time
(PST) |
|---|
| any time | UTC - 5 hrs. | UTC - 6 hrs. | UTC - 7 hrs. | UTC - 8 hrs. |
| 00:00 (midnight) | 19:00 (7 pm) | 18:00 (6 pm) | 17:00 (5 pm) | 16:00 (4 pm) |
| 12:00 (noon) | 7:00 (7 am) | 6:00 (6 am) | 5:00 (5 am) | 4:00 (4 am) |
| Data Type |
Variables |
Forecasted/
Observed |
Frequency |
| Surface
Meteorological |
Wind speed, wind direction,
temperature, relative humidity, solar radiation, cloud cover, visibility,
pressure |
Observed |
Hourly |
| Surface
Air Quality |
Ozone, nitrogen oxides,
carbon monoxide, volatile organic compounds |
Observed |
Hourly |
| Upper
air meteorology (rawindsondes, radar profilers, and sodars) |
Vertical profiles of
wind speed, wind direction, temperature, relative humidity |
Observed |
Twice-per-day
to hourly |
| Aloft
air quality observations (towers, mountains, and aircraft) |
Ozone, nitrogen oxides |
Observed |
Variable |
| Weather
charts |
Surface: wind speed,
wind direction, temperature, relative humidy, pressure
850-mb: wind speed, wind direction, temperature, height
700-mb: wind speed, wind direction, temperature, height
500-mb: wind speed, wind direction, temperature, height, others
|
Forecasted
and observed |
Twice
per day |
| Weather
radar |
Precipitation |
Observed |
Hourly |
| Satellite |
Cloud cover (visible
and infrared) |
Observed |
Hourly
and/or sub-hourly |
| Meteorological
model forecasts |
Temperature, relative
humidity, wind speed, wind direction, cloud cover, visibility, precipitation,
others at many levels |
Forecasted |
Twice
per day |
| Text
weather forecasts |
Discussions |
Forecasted
and observed |
Four
or more times per day |
Back to the Table of Contents
| Types of Clouds |
Image Type |
Interpretation |
| Low Clouds |
|
Visible
|
|
Infrared/Enhanced Infrared
|
| Water Vapor |
|
| Low clouds look bright on visible images, since a significant amount
of light is radiated back to the atmosphere. If you notice, most low
clouds have a very dark base, signifying that light is not getting
through to the surface. |
| Low clouds appear gray on IR/EnhIR images, since the tops of low
clouds are relatively warm. |
| Since low clouds are so low in the atmosphere, they are detectable
on water vapor images. |
|
| Cirrus Clouds |
| Visible |
| Infrared/Enhanced Infrared |
| Water Vapor |
|
| Cirrus clouds look a bit off-white in color, as compared with the
brighter images of low clouds. Cirrus clouds as seen from the surface
look white, meaning that light is getting through. Some light, however,
is scattered back to the atmosphere, so the images appear as the characteristic
off-white color. |
| Cirrus clouds are quite high in the atmosphere, so they are quite
cold. On IR images, cirrus clouds appear bright white in color. |
| The high-altitude crystals that are found in cirrus clouds appear
as white on water vapor images. |
|
|
Tall Cumulus
Cumulonimbus
|
| Visible |
| Infrared/Enhanced Infrared |
| Water Vapor |
|
| These clouds appear as bright white on visible images, since a significant
amount of radiation is reflected or scattered back to the atmosphere. |
| The tops of these clouds are quite cold, so they appear as bright
white on IR/EnhIR images. |
| As with cirrus clouds, these clouds emit cold (6.7 micron) radiation,
so they appear as white images on water vapor images. |
|
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