Occasional Thoughts on Climate Change

[donsutherland1]

45 minutes ago, rclab said:

To educate/help the non professional (and I don’t mean not intelligent) descriptive terms like heat dine are preferable to ‘ mid-tropospheric ridges’. When you’re trying to get the public’s attention on heart health would you talk about the potential of getting a ‘widow maker’ or a mycardio infarction. Which one is likely to keep the pedestrian reading? In either case both sides of the equation is equal. 
it’s actually good to have a person of different opinion in a group as a leavening agent. Providing  that all discussions and retorts are civil and not just superficial. For that reason, during a period of time when our sub forum area may face a cold season event I look to read S19’s thought. and forky’s along with, like yourself, other well versed members..if all else fails I just listen to the ballad Turn, Turn, Turn and straighten myself out. Stay well, as always ……

 

Yes, that's a key point. Good communication is essential in a field like meteorology. Even if one might prefer to use a different term, one shouldn't portray one's preference as a requirement, especially when one's own profession recognizes the term one objects to. 

[TheClimateChanger]

On 8/24/2025 at 8:01 AM, bluewave said:

Yeah, this has been the opposite of the Dust Bowl pattern over the last decade. Record summer warmth in the West and East with less warm over the middle section of the CONUS. The Dust Bowl pattern had the record summer heat in the middle and cooler along both coasts. 

 

Funny, you don't see Bastardi trot out his population-weighted metrics in recent summers. Loves to pop them out when there's a trough in the east though.

[TheClimateChanger]

On 8/22/2025 at 6:30 PM, LibertyBell said:

But heat increase is measured by rising temperatures, not dew points.

Q: How about ignoring the human aspect? Which one carried more total heat? A temp of 92F, and dewpoint of 75F, or a temp. of 104F, and dewpoint of 50F?

 

 

To determine which condition carries more total heat, ignoring the human aspect, we need to evaluate the total energy content of the air, which depends on both temperature and moisture content. The enthalpy of the air, which measures the total heat (sensible heat from temperature plus latent heat from moisture), is the appropriate metric. Wet bulb temperature can help approximate this, but we’ll calculate enthalpy directly using the given temperatures and dewpoints.Given Conditions:

1. Condition 1: Dry bulb temperature = 92°F, Dewpoint = 75°F
2. Condition 2: Dry bulb temperature = 104°F, Dewpoint = 50°F

Step 1: Understand the Components

• Dry bulb temperature reflects the sensible heat (energy associated with temperature).
• Dewpoint indicates the moisture content, which relates to latent heat (energy tied to water vapor).
• Higher dewpoint means more moisture, contributing to latent heat, while higher dry bulb temperature increases sensible heat.
• Enthalpy (in Btu/lb of dry air) combines both sensible and latent heat and is commonly used in psychrometrics to compare total heat content.

Step 2: Approximate Enthalpy CalculationEnthalpy of moist air can be calculated using the formula:

h=0.24⋅T+W⋅(1061+0.444⋅T)h = 0.24 \cdot T + W \cdot (1061 + 0.444 \cdot T)h = 0.24 \cdot T + W \cdot (1061 + 0.444 \cdot T)

where:

• ( h ) is enthalpy (Btu/lb of dry air),
• ( T ) is dry bulb temperature (°F),
• ( W ) is the humidity ratio (lb of water vapor per lb of dry air),
• 0.24 is the specific heat of dry air (Btu/lb·°F),
• 1061 is the latent heat of vaporization of water (Btu/lb at 0°F),
• 0.444 is the specific heat of water vapor (Btu/lb·°F).

The humidity ratio ( W ) depends on the dewpoint, which determines the vapor pressure of water in the air. We can estimate ( W ) using the saturation pressure at the dewpoint and the atmospheric pressure (assumed standard at 14.696 psia or 101.325 kPa).Step 2a: Calculate Humidity RatioThe humidity ratio is given by:

W=0.62198⋅PvP−PvW = \frac{0.62198 \cdot P_v}{P - P_v}W = \frac{0.62198 \cdot P_v}{P - P_v}

where:

• PvP_vP_v
  is the vapor pressure at the dewpoint (psia),
• ( P ) is atmospheric pressure (14.696 psia).

The vapor pressure

PvP_vP_v

can be approximated using the Antoine equation or simplified correlations for saturation pressure at the dewpoint temperature. A common approximation for saturation pressure (in psia) over liquid water is:

Pv=exp⁡(20.386−5132Td+459.67)P_v = \exp\left(20.386 - \frac{5132}{T_d + 459.67}\right)P_v = \exp\left(20.386 - \frac{5132}{T_d + 459.67}\right)

where

TdT_dT_d

is the dewpoint in °F, and

Td+459.67T_d + 459.67T_d + 459.67

converts to °R (Rankine).Condition 1: Dewpoint = 75°F

• Td=75°FT_d = 75°FT_d = 75°F
  , so
  Td+459.67=534.67°RT_d + 459.67 = 534.67°RT_d + 459.67 = 534.67°R
  .
• Pv=exp⁡(20.386−5132534.67)≈exp⁡(20.386−9.599)≈exp⁡(10.787)≈0.487 psiaP_v = \exp\left(20.386 - \frac{5132}{534.67}\right) \approx \exp(20.386 - 9.599) \approx \exp(10.787) \approx 0.487 \, \text{psia}P_v = \exp\left(20.386 - \frac{5132}{534.67}\right) \approx \exp(20.386 - 9.599) \approx \exp(10.787) \approx 0.487 \, \text{psia}
  .
• W=0.62198⋅0.48714.696−0.487≈0.302914.209≈0.0213 lb water/lb dry airW = \frac{0.62198 \cdot 0.487}{14.696 - 0.487} \approx \frac{0.3029}{14.209} \approx 0.0213 \, \text{lb water/lb dry air}W = \frac{0.62198 \cdot 0.487}{14.696 - 0.487} \approx \frac{0.3029}{14.209} \approx 0.0213 \, \text{lb water/lb dry air}
  .

Condition 2: Dewpoint = 50°F

• Td=50°FT_d = 50°FT_d = 50°F
  , so
  Td+459.67=509.67°RT_d + 459.67 = 509.67°RT_d + 459.67 = 509.67°R
  .
• Pv=exp⁡(20.386−5132509.67)≈exp⁡(20.386−10.071)≈exp⁡(10.315)≈0.300 psiaP_v = \exp\left(20.386 - \frac{5132}{509.67}\right) \approx \exp(20.386 - 10.071) \approx \exp(10.315) \approx 0.300 \, \text{psia}P_v = \exp\left(20.386 - \frac{5132}{509.67}\right) \approx \exp(20.386 - 10.071) \approx \exp(10.315) \approx 0.300 \, \text{psia}
  .
• W=0.62198⋅0.30014.696−0.300≈0.186614.396≈0.0130 lb water/lb dry airW = \frac{0.62198 \cdot 0.300}{14.696 - 0.300} \approx \frac{0.1866}{14.396} \approx 0.0130 \, \text{lb water/lb dry air}W = \frac{0.62198 \cdot 0.300}{14.696 - 0.300} \approx \frac{0.1866}{14.396} \approx 0.0130 \, \text{lb water/lb dry air}
  .

Step 2b: Calculate Enthalpy Condition 1: 92°F, Dewpoint 75°F

• T=92°FT = 92°FT = 92°F
  ,
  W=0.0213W = 0.0213W = 0.0213
  .
• Sensible heat:
  0.24⋅92=22.08 Btu/lb0.24 \cdot 92 = 22.08 \, \text{Btu/lb}0.24 \cdot 92 = 22.08 \, \text{Btu/lb}
  .
• Latent heat term:
  W⋅(1061+0.444⋅92)=0.0213⋅(1061+40.848)≈0.0213⋅1101.848≈23.47 Btu/lbW \cdot (1061 + 0.444 \cdot 92) = 0.0213 \cdot (1061 + 40.848) \approx 0.0213 \cdot 1101.848 \approx 23.47 \, \text{Btu/lb}W \cdot (1061 + 0.444 \cdot 92) = 0.0213 \cdot (1061 + 40.848) \approx 0.0213 \cdot 1101.848 \approx 23.47 \, \text{Btu/lb}
  .
• Total enthalpy:
  h=22.08+23.47=45.55 Btu/lbh = 22.08 + 23.47 = 45.55 \, \text{Btu/lb}h = 22.08 + 23.47 = 45.55 \, \text{Btu/lb}
  .

Condition 2: 104°F, Dewpoint 50°F

• T=104°FT = 104°FT = 104°F
  ,
  W=0.0130W = 0.0130W = 0.0130
  .
• Sensible heat:
  0.24⋅104=24.96 Btu/lb0.24 \cdot 104 = 24.96 \, \text{Btu/lb}0.24 \cdot 104 = 24.96 \, \text{Btu/lb}
  .
• Latent heat term:
  W⋅(1061+0.444⋅104)=0.0130⋅(1061+46.176)≈0.0130⋅1107.176≈14.39 Btu/lbW \cdot (1061 + 0.444 \cdot 104) = 0.0130 \cdot (1061 + 46.176) \approx 0.0130 \cdot 1107.176 \approx 14.39 \, \text{Btu/lb}W \cdot (1061 + 0.444 \cdot 104) = 0.0130 \cdot (1061 + 46.176) \approx 0.0130 \cdot 1107.176 \approx 14.39 \, \text{Btu/lb}
  .
• Total enthalpy:
  h=24.96+14.39=39.35 Btu/lbh = 24.96 + 14.39 = 39.35 \, \text{Btu/lb}h = 24.96 + 14.39 = 39.35 \, \text{Btu/lb}
  .

Step 3: Compare Total Heat

• Condition 1: 92°F, dewpoint 75°F → Enthalpy ≈ 45.55 Btu/lb.
• Condition 2: 104°F, dewpoint 50°F → Enthalpy ≈ 39.35 Btu/lb.

ConclusionThe air at 92°F with a dewpoint of 75°F carries more total heat (enthalpy = 45.55 Btu/lb) than the air at 104°F with a dewpoint of 50°F (enthalpy = 39.35 Btu/lb). The higher moisture content (higher dewpoint) in Condition 1 contributes significantly to its latent heat, outweighing the higher sensible heat from the higher temperature in Condition 2.Thus, 92°F with a dewpoint of 75°F has more total heat.