I saw this and liked how it echoes with my post. Science is hard. On Sat, Oct 5, 2024 at 1:00 PM Nicholas Thompson <thompnicks...@gmail.com> wrote:
> > After bullying GeorgeIV for a couple hours, I got this superb answer out > of him. > > *Summary:* > > In *pseudo-adiabatic calculations*, we disregard: > > - *Condensed water retained in the parcel* (assuming it falls out as > precipitation), > - *Precipitation drag* (the downward resistance of falling > precipitation), > - *Heat transfer between the parcel and the environment* (except > latent heat release). > > These variables are considered *trivial* relative to the dominant forces > in convective storms, especially the *latent heat release* from > condensation, which drives strong updrafts and is the primary factor > determining the parcel’s buoyancy. > > Does this clarify the role of simplifications in pseudo-adiabatic > processes? Would you like to go deeper into any specific part of this? > > *You said:* > > Ok. Now this all makes sense. But compare your most recent answer to ones > you made earlier which seemed to suggest that the latent heat released by > condensation (in addition to the condensed water) is lost to the parcel. No > heat is lost to the parcel, only mass, and that mass is trivial by > comparision with the total mass of the parcel since even most air contains > relatively little mass of water. > > *ChatGPT said:* > > ChatGPT > > You're absolutely right, and I can see how my earlier answers might have > created some confusion. Let's clear that up, focusing on the distinction > between *latent heat* and *condensate (water)* in pseudo-adiabatic > processes. > > *Correct Understanding: No Heat is Lost from the Parcel, Only Mass* > > In a *pseudo-adiabatic process*, the *latent heat released by > condensation* is *not lost* from the air parcel. It remains in the parcel > and directly contributes to: > > - *Warming the parcel*: The *latent heat* released when water vapor > condenses into liquid (or ice) *warms* the parcel, slowing the rate at > which it cools as it rises. This additional warmth keeps the parcel *more > buoyant* compared to its surroundings. > > What *is lost*, however, is the *condensate*: > > - *Mass loss*: The condensed water (in liquid or ice form) is assumed > to *precipitate out* of the parcel. This *reduces the total mass* of > the parcel but has a relatively small impact on the overall mass, since > even in moist air, the water vapor content is small compared to the air’s > mass. As a result, the *mass loss from precipitation* is considered > *trivial* relative to the total parcel mass, but it is a > simplification made for the sake of easier calculation. > > *Earlier Miscommunication: What Happens to Latent Heat?* > > In my earlier explanation, I might have implied that both the *condensate* > and the *latent heat* are somehow lost from the parcel in the > pseudo-adiabatic process. That’s not the case. The *latent heat* stays > with the parcel—it’s only the *water droplets (or ice crystals)* that are > assumed to fall out. > > *Why This Matters:* > > 1. *Buoyancy*: The *latent heat* remains inside the parcel, increasing > its *temperature* and *buoyancy* as it rises. This helps the parcel > remain *warmer* than the surrounding air, driving the upward motion. > 2. *Mass Loss is Small*: As you correctly pointed out, the *mass of > water vapor* in a parcel is generally small relative to the *total > mass* of the air parcel (which consists mostly of nitrogen and > oxygen). Even in very humid conditions, water vapor usually makes up only a > few percent of the total mass of the air. So, the *mass lost to > precipitation* is *trivial* when compared to the overall mass of the > parcel. > > *Summary of Correct Picture:* > > - *Latent heat*: *Remains within the parcel*, keeping it warm and > buoyant. > - *Condensate*: Assumed to fall out of the parcel, leading to *mass > loss*. > - *Mass loss is small*: Even though the mass of the parcel decreases > due to precipitation, it is considered *trivial* relative to the total > mass of the parcel. > > In the *pseudo-adiabatic process*, the *main focus is on the latent heat* > retained by the parcel, as this is what maintains buoyancy. The loss of > mass due to precipitation is simplified for ease of calculation but is > relatively minor in the big picture of atmospheric processes. > -- > Nicholas S. Thompson > Emeritus Professor of Psychology and Ethology > Clark University > nthomp...@clarku.edu > https://wordpress.clarku.edu/nthompson >
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