3.5: Alternative Text Descriptions for Investigation 3

Figure 3.2.1: Surface Air Temperature data

This is a surface air temperature map of the continental United States, showing temperatures in degrees Fahrenheit at various weather stations. The map is valid for 06 Z (2:00 AM EDT) on July 6, 2020, and was produced by the NWS/NOAA (National Weather Service/National Oceanic and Atmospheric Administration).

General Layout:

• The map outlines each of the 48 contiguous U.S. states with numerical temperature values displayed at station locations.
• All temperatures are shown in plain black numerals, distributed across the country without any color shading.
• Temperatures range from the 60s°F in the northern tier to over 100°F in the Southwest, especially in the desert regions.

Regional Highlights:

• Western U.S.:
  • California and Arizona show extremely high temperatures, including 110°F in southeastern California and 102°F in southern Arizona.
  • Nevada, Utah, and New Mexico report widespread temperatures in the 90s.
  • Pacific Northwest is cooler, with readings in the 60s to 70s.
• Central U.S.:
  • States like Kansas, Oklahoma, and Texas show temperatures in the 80s and low 90s.
  • Colorado and Wyoming exhibit a broader range, from 70s in the north to upper 80s and 90s in the south.
• Eastern U.S.:
  • Temperatures are mostly in the 70s and 80s, with cooler readings (mid-60s to low 70s) along parts of the Appalachians and Northeast coast.
  • Southeast states (Florida, Georgia, Alabama) show temperatures in the upper 70s to mid-80s, with Florida reporting 86°F to 88°F.
• Northern Plains and Great Lakes Region:
  • Temperatures are generally cooler, ranging from 60°F to 75°F, with the Upper Midwest seeing some temperatures below 70°F.

Figure 3.2.2: Surface Air Temperature data with isotherms

This is a surface temperature map of the continental United States, valid for 01Z on July 6, 2020, and includes both temperature observations (in °F) and isotherms (contour lines of equal temperature). 

Key Features:

• Numerical temperature values are displayed at numerous observation points across the U.S., representing air temperatures in degrees Fahrenheit.
• Lines on the map are labeled isotherms, representing contours of equal temperature, drawn at 10°F intervals.
• The isotherms create closed loops and bands across the map, visually depicting temperature gradients and regional heat patterns.

Regional Observations:

• Southwest U.S. (California, Arizona, Nevada)
  • The hottest region on the map, with isotherms for 90°F, 100°F, and 110°F clearly marked.
  • Southern California and Arizona show stations with temperatures as high as 110°F to 112°F.
  • Dense packing of isotherms indicates a steep temperature gradient.
• Central and Southern Plains (Texas, Oklahoma, Kansas):
  • A broad area enclosed by 90°F and 100°F isotherms, with many stations reporting temperatures between 90°F and 100°F.
  • An enclosed "bullseye" region in southern Texas suggests localized peak temperatures.
• Midwest and Great Plains:
  • Isotherms span from 80°F to 90°F, curving through states like Nebraska, Iowa, and Illinois.
  • Cooler readings of 70°F to 80°F are found in parts of Colorado and the northern Midwest.
• Southeast and East Coast
  • Generally warm and uniform, with most stations between 80°F and 90°F.
  • Isotherms are more widely spaced, indicating weaker temperature gradients.
• Pacific Northwest and Northern Rockies:
  • Cooler regions, with isotherms indicating 60°F to 70°F, especially in higher elevations and coastal zones

Figure 3.3.1: Advection shown using isotherms and wind barbs

This diagram illustrates temperature advection using simplified station models and isotherms (lines of equal temperature).

Visual Elements:

• Station Models:
  • Each station is represented by a circle with a wind barb extending from it, pointing in the direction wind is coming from.
  • The length and shape of the barbs suggest wind speed (not numerically labeled).
• Contour Lines (Isotherms):
  • There are five curved, horizontal lines labeled 50, 60, 70, and 80, denoting temperature in degrees Fahrenheit.
  • These lines curve from upper left to lower right, separating areas of different surface temperature.
• Wind Patterns and Zones:
  • Winds in region A (left) mostly flow parallel to isotherms, indicating little to no temperature advection.
  • Winds in region B (center) are crossing isotherms from cooler to warmer zones (from left to right), suggesting warm air advection.
  • Winds in region C (right) are flowing from warmer to cooler zones, indicating cold air advection.
• Labels:
  • Three large capital letters—A, B, and C, marking different zones for interpretation.

Figure 3.3.2: Simplified map of Isotherms, Fronts, and Wind Barbs

This hand-drawn weather map of the continental United States shows surface isotherms, a cold front, and wind barbs, along with labels A through F marking specific city locations for analysis. The image is instructional, highlighting the spatial relationship between wind direction and temperature fields.

Key Elements:

• Isotherms (Lines of Equal Temperature)
  • Curved lines are labeled 40°F, 50°F, 60°F, and 70°F.
  • These lines span from the Southwest (California and Texas) to the Northeast, marking areas of consistent surface temperature.
• Cold Front:
  • A line with triangles pointing eastward stretches from eastern Texas to the Midwest, indicating the location of a cold front.
• Labeled Cities (A–F):
  • The map uses letters A through F to indicate six city locations, each placed to illustrate how local wind barbs relate to surrounding isotherms.
• Wind Barb Interpretation at Each City:
  • City A (Eastern Texas): Wind barb is oriented perpendicular to the isotherms, blowing across them from lower to higher temperature values.
  • City B (Georgia): Wind barb is angled moderately across the isotherms, not fully perpendicular, but still cutting across several temperature contours.
  • City C (Kentucky/Tennessee area): Wind barb is nearly parallel to the isotherms, indicating little directional crossing between temperature zones.
  • City D (Oklahoma): Wind barb is oriented sharply across the isotherms, intersecting them at a steep angle from cooler to warmer values.
  • City E (Southern Wisconsin / Chicago area): Wind barb is almost perpendicular to the isotherms, intersecting multiple temperature lines in a short distance.
  • City F (Northeastern U.S.): Wind barb is angled across isotherms, showing a noticeable but not steep cross-contour flow.

Interpretation:

• The map demonstrates temperature advection, particularly in the context of a frontal boundary.
  • Warm air advection occurs ahead of the cold front, where southerly winds cross isotherms from warmer to cooler areas.
  • Cold air advection occurs behind the front, where northwesterly winds transport cooler air into warmer regions.
• The curvature and spacing of isotherms, combined with wind direction, help visualize where warming or cooling is occurring at the surface.

Figure 3.3.3: Isotherms, Station Models, and Fronts

This image is a detailed surface weather analysis map of the continental United States, valid at 13Z (8:00 AM EST) on February 8, 2017. It shows isotherms, surface fronts, station data, and areas of high and low pressure.

Key Elements:

• Isotherms (lines of equal temperature):
  • Labeled in 10°F increments (e.g., 20, 30, 40, 50, 60, 70).
  • These lines curve across the country, helping visualize temperature gradients and regions of advection.
• Surface Fronts:
  • A cold front extends from Arkansas to New York, pushing southeastward. It features triangle markers pointing in the direction of movement.
  • A warm front connects to a low-pressure center in the eastern U.S.
  • An occluded front is visible near the northeastern states.
  • A stationary front in the central U.S. marks the boundary between different air masses.
• Highs and Lows (H and L Symbols):
  • Hs denote areas of high pressure, found in parts of the West, Northern Rockies, and Midwest.
  • Ls mark low-pressure centers, including one in the Southern Plains and another off the Pacific Northwest coast.
• Station Models (Black Symbols):
  • Small circular plots represent weather stations, showing temperature, wind barbs, cloud cover, and pressure trends.
  • Temperatures range from single digits (°F) in the northern Plains to 60s and 70s in the Southeast.
• Specific Wind Barbs:
  • New Orleans, Louisiana: The wind barb shows a south wind at 10 knots, indicated by a single full barb pointing straight upward (from the south).
  • Sioux City, Iowa: The wind barb shows a north-northwest wind at 25 knots, indicated by two full barbs and one half barb, with the shaft pointing from the northwest toward the station. 
• Regional Highlights:
  • Cold Arctic air is present in the Upper Midwest and Northern Plains, with temperatures as low as single digits Fahrenheit and tightly packed isotherms.
  • Mild, moist air is present in the Southeast, with temperatures above 60°F and widespread southerly flow ahead of the cold front.
  • Strong temperature advection is evident where winds cross isotherms, especially near and ahead of the cold front in the ea stern U.S.