ForHosting KIT · Science

Atmospheric moisture flux calculator

Air holding 0.01 kg of water vapor per kg and moving at 10 m/s carries a horizontal moisture flux of 0.1, the product of specific humidity and wind. A quick, transparent figure for homework, logger records and first-order moisture budgets. Free in your browser.

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Run — free How it works & API

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Worked example

If you enter

Specific humidity: 0.01
Wind speed: 10

You get

Moisture flux: 0.1
Flux: 0.1

Horizontal moisture flux quantifies how much water vapor is carried by the wind—a central diagnostic in atmospheric science, hydrology, and climate analysis. Given specific humidity as a mass fraction of water vapor in moist air and a horizontal wind speed (or directed wind component) in metres per second, this atmospheric moisture flux calculator multiplies them to produce the scalar flux F equals q times U. Students use it to check textbook problems; researchers and engineers use it as a lightweight, deterministic step inside pipelines that map humidity and wind fields into transport estimates. Negative specific humidity is rejected as non-physical, and non-numeric wind speed fails validation instead of silently becoming NaN.

What horizontal moisture flux means and the formula F = q · U

Specific humidity q is the mass of water vapor divided by the mass of moist air, expressed as a dimensionless mass fraction with SI-consistent units of kilograms per kilogram. Horizontal wind speed U is the speed of air motion in the horizontal plane, or—when you need directed transport—a signed wind component along a chosen axis, both in metres per second.

Their product F equals q times U is the simplest scalar measure of horizontal water vapor flux used in teaching, field screening, and many first-order moisture-transport budgets: it tells you how much water-vapor mass fraction is advected per unit time along the wind. When U is a magnitude, F is non-negative for physical q greater than or equal to zero. When U is a signed component (for example the zonal wind u), the sign of F indicates the direction of moisture transport relative to that axis.

This calculator does not integrate through the atmospheric column, does not multiply by air density, and does not resolve vertical motion: those steps belong to denser analysis workflows. It does give a transparent, reproducible value of F that you can post-process, scale by density, or integrate later.

Where an atmospheric moisture flux calculator earns its keep

Meteorology courses and climate labs need a fast oracle for F equals q times U so learners can verify homework without a full reanalysis stack. Hydrology and agricultural models often take surface humidity and wind as inputs to estimate horizontal moisture advection into a catchment or greenhouse boundary layer. Field campaigns that log humidity sensors and anemometers can batch-convert paired readings into transport diagnostics before denser post-processing.

Failed validation does not consume balance.

What you can do with it

Classroom and lab checks

Let students submit specific humidity and wind speed and verify the horizontal moisture flux F = q · U against textbook worked examples.

Field logger batch conversion

Turn paired humidity and anemometer records into scalar moisture-transport values before denser analysis or density scaling.

Hydrology and boundary-layer screening

Estimate first-order horizontal water vapor advection into a domain from observed q and U without a full atmospheric model.

FAQ

What happens if specific humidity is negative?

A negative mass fraction of water vapor is non-physical and is not billed.

What if wind speed is non-numeric?

Only finite numbers (or numeric strings) are accepted.

Does this include air density or column integration?

Multiply by density or integrate vertically in your own pipeline if you need mass flux density or IVT.

Can I enter a wind component instead of wind speed?

Yes. Use a signed component along a chosen axis, such as the west-to-east wind, and the sign of the result shows which way moisture moves along that axis. With a plain wind speed the flux stays positive.

In what units do I enter specific humidity?

As a mass fraction in kilograms of water vapor per kilogram of moist air, so 0.01 means one hundredth of the air's mass is vapor. The wind goes in metres per second.

Related tools

For developers — API access

Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.

API endpoint

POSThttps://api.kit.forhosting.com/earth/moisture-flux

Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.

Call it from your stack

curl -X POST https://api.kit.forhosting.com/earth/moisture-flux \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"specific_humidity":0.01,"wind_speed":10}'

const res = await fetch("https://api.kit.forhosting.com/earth/moisture-flux", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "specific_humidity": 0.01,
    "wind_speed": 10
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/earth/moisture-flux",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "specific_humidity": 0.01,
    "wind_speed": 10
},
)
task_id = res.json()["task_id"]

<?php
$res = file_get_contents("https://api.kit.forhosting.com/earth/moisture-flux", false, stream_context_create([
  "http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
    "content" => '{"specific_humidity":0.01,"wind_speed":10}',
  ],
]));
$task = json_decode($res, true);

body := bytes.NewBufferString(`{"specific_humidity":0.01,"wind_speed":10}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/earth/moisture-flux", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "specific_humidity": 0.01,
  "wind_speed": 10
}

Example response

{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "earth.moisture_flux",
  "status": "queued",
  "_links": {
    "result": "/tasks/tsk_…/result"
  }
}

The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.

Pricing

Per request$0.002

Published price — no tokens, no invented credits. A failed task is never charged.

Errors

HTTP	Code	Meaning
`401`	`unauthorized`	Missing or invalid API key.
`402`	`insufficient_balance`	Your balance doesn't cover the task price.
`404`	`unknown_type`	That task type doesn't exist.
`429`	`rate_limited`	Too many requests. Use the webhook instead of polling.

Technical notes

Input contract, response fields, and validation errors

Specific humidity must be greater than or equal to zero: a negative mass fraction of water vapor is non-physical and is rejected with a clear message. Wind speed must be numeric and finite; the capability message explicitly treats non-numeric wind as invalid rather than coercing it. Example: specific humidity zero point zero one with wind speed ten metres per second yields moisture flux zero point one. Invalid requests are not billed. POST a JSON body with two required finite numbers: specific_humidity (aliases q, humidity_specific, sh, specific_hum, humidity) and wind_speed (aliases wind, u, speed, velocity, wind_velocity, wind_speed_ms). Each field may arrive as a JSON number or as a numeric string; empty strings, missing fields, and non-numeric values fail with invalid_input naming the field. On success the body echoes specific_humidity and wind_speed, returns moisture_flux and the alias flux (both equal to q times U, rounded), a formula string restating F equals q times U, and unit set to (kg/kg)·(m/s). Pair the result with your own density field if you need mass flux density in kilograms per square metre per second; multiply F by air density outside this endpoint.

Where an atmospheric moisture flux calculator earns its keep

Content sites that rank for atmospheric moisture flux calculator benefit from a live free browser tool whose arithmetic matches the prepaid API at $0.002 per successful call.

Technical questions

How is horizontal moisture flux calculated?

Send finite specific_humidity q (kg/kg, ≥ 0) and wind_speed U (m/s). The API returns F = q · U as moisture_flux (and flux), with unit (kg/kg)·(m/s).

What does the atmospheric moisture flux calculator cost?

The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.

Read the full KIT documentation →

Run — free

Worked example

What horizontal moisture flux means and the formula F = q · U

Where an atmospheric moisture flux calculator earns its keep

What you can do with it

Classroom and lab checks

Field logger batch conversion

Hydrology and boundary-layer screening

FAQ

Related tools

For developers — API access

API endpoint

Call it from your stack

Example request

Example response

Pricing

Errors

Technical notes

Input contract, response fields, and validation errors

Where an atmospheric moisture flux calculator earns its keep

Technical questions

thank you