wet-bulb depression: meaning, definition, pronunciation and examples
Very RareTechnical, Scientific
Quick answer
What does “wet-bulb depression” mean?
A specific technical term in meteorology and thermodynamics for the difference between the dry-bulb air temperature and the lower wet-bulb temperature, used to assess humidity and evaporative cooling potential.
Audio
Pronunciation
Definition
Meaning and Definition
A specific technical term in meteorology and thermodynamics for the difference between the dry-bulb air temperature and the lower wet-bulb temperature, used to assess humidity and evaporative cooling potential.
The numeric difference, measured in degrees, between the temperature measured by a standard thermometer (dry bulb) and one with a water-saturated wick (wet bulb); a crucial indicator of heat stress in biological and industrial contexts, and a key parameter in psychrometric charts.
Dialectal Variation
British vs American Usage
Differences
Usage is identical across both variants in technical contexts. Spelling differences (e.g., 'humidity' vs. 'humidity') do not apply to the term itself. Potential minor differences in associated jargon (e.g., 'heat stress index' vs. 'heat index') but 'wet-bulb depression' is standard globally.
Connotations
Neutral and purely technical in both regions.
Frequency
Extremely rare outside of specific professional or academic fields like meteorology, HVAC engineering, occupational health, and climatology. Frequency is essentially identical in UK and US technical publications.
Grammar
How to Use “wet-bulb depression” in a Sentence
The wet-bulb depression (V) is (Adj) / measures (Num).One can/cannot calculate (V) the wet-bulb depression (O) from (Prep) the dry-bulb temperature.A high wet-bulb depression (S) indicates (V) low humidity (O).Vocabulary
Collocations
Examples
Examples of “wet-bulb depression” in a Sentence
verb
British English
- (Not applicable; the term is exclusively a noun phrase)
American English
- (Not applicable; the term is exclusively a noun phrase)
adverb
British English
- (Not applicable)
American English
- (Not applicable)
adjective
British English
- (Not applicable; 'wet-bulb' is itself a noun acting as a modifier)
American English
- (Not applicable; 'wet-bulb' is itself a noun acting as a modifier)
Usage
Meaning in Context
Business
Unused, except in highly specialised industries related to climate control, agriculture, or workplace safety.
Academic
Common in meteorology, environmental science, engineering, and human physiology papers discussing heat stress and humidity.
Everyday
Virtually never used. An everyday speaker would describe the concept as 'the difference between the regular and the 'wet' thermometer readings'.
Technical
The primary register. Used in weather reports for specialists, HVAC system design, occupational safety assessments, and scientific research on climate.
Vocabulary
Synonyms of “wet-bulb depression”
Neutral
Weak
Vocabulary
Antonyms of “wet-bulb depression”
Watch out
Common Mistakes When Using “wet-bulb depression”
- Writing 'wet bulb-depression' (incorrect hyphenation).
- Confusing it with 'dew point depression' (a different, though related, measure).
- Using 'wet-bulb' as a standalone noun to mean the depression (e.g., 'The wet-bulb was high today').
FAQ
Frequently Asked Questions
No, it is a related but distinct measure. Wet-bulb depression is a temperature difference (in °C or °F). Relative humidity is a percentage. A high wet-bulb depression corresponds to low humidity, and a low depression corresponds to high humidity.
It is a key factor in heat stress. A low wet-bulb depression (meaning high humidity) means sweat cannot evaporate effectively, preventing the body from cooling itself, which can lead to dangerous conditions like heatstroke.
It is measured using a psychrometer, an instrument with two identical thermometers. One has its bulb exposed to the air (dry bulb). The other has its bulb kept moist with a wick (wet bulb). The difference in their readings is the wet-bulb depression.
Yes. A wet-bulb depression of zero occurs when the air is saturated with water vapour (100% relative humidity). At this point, no evaporation can occur, so the wet-bulb and dry-bulb temperatures are identical.
A specific technical term in meteorology and thermodynamics for the difference between the dry-bulb air temperature and the lower wet-bulb temperature, used to assess humidity and evaporative cooling potential.
Wet-bulb depression is usually technical, scientific in register.
Wet-bulb depression: in British English it is pronounced /ˌwet bʊlb dɪˈpreʃ.ən/, and in American English it is pronounced /ˌwet bʊlb dɪˈpreʃ.ən/. Tap the audio buttons above to hear it.
Learning
Memory Aids
Mnemonic
Imagine a thermometer with a sad, wet sock on its bulb. The 'depression' is how much its temperature reading is lowered (depressed) compared to the dry, happy thermometer next to it.
Conceptual Metaphor
TEMPERATURE IS HEIGHT/VERTICAL POSITION (thus a 'depression' is a lowering).
Practice
Quiz
What does 'wet-bulb depression' directly measure?