Inches per hour (in/h) to Millimeters per hour (mm/h) conversion

What is inches per hour?

What is Inches per hour?

Inches per hour (in/h) is a unit of speed, specifically measuring the distance traveled in inches over a period of one hour. It's commonly used to express very slow speeds or rates, such as the growth rate of plants, the movement of glaciers, or, most frequently, the rate of precipitation.

Understanding Inches per Hour

Definition

Inches per hour (in/h) is a unit of velocity expressing the distance traveled in inches for every hour.

How it's formed

The unit is formed by dividing a distance measured in inches by a time measured in hours.

$$\text{Speed (in/h)} = \frac{\text{Distance (inches)}}{\text{Time (hours)}}$$

Applications and Examples

Precipitation Rate

Inches per hour is most commonly used to measure the intensity of rainfall.

• Light rain: Typically less than 0.10 in/h.
• Moderate rain: Between 0.10 and 0.30 in/h.
• Heavy rain: More than 0.30 in/h.

You can read more about rate of precipitation from National Weather Service website.

Plant Growth

The growth rate of plants, especially shoots or roots, can be measured in inches per hour, particularly for time-lapse studies or under controlled conditions. For example, certain types of bamboo can grow several inches per hour under optimal conditions.

Glacial Movement

While glaciers typically move very slowly, their movement can be measured in inches per hour over short periods. This is especially true during surges or periods of rapid melting.

Manufacturing Processes

In certain manufacturing or machining processes, the feed rate (how fast a cutting tool moves) might be expressed in inches per hour, especially for very precise or slow operations.

What is Millimeters per hour?

Millimeters per hour (mm/h) is a unit of measurement for precipitation intensity, specifically quantifying the amount of liquid precipitation (usually rain) that falls over a period of one hour. It indicates the depth of water that would accumulate on a level surface if the precipitation remained there and did not run off, infiltrate, or evaporate.

Understanding Millimeters per Hour

• Definition: Millimeters per hour expresses the rate at which rain, snow, or other liquid precipitation accumulates. A higher value indicates heavier precipitation.
• Formation: It is derived by measuring the amount of precipitation collected over a specific time period (one hour) and expressing it in terms of millimeters.
• Practical Interpretation: 1 mm/h means that if the rain fell steadily for an hour and didn't go anywhere, it would form a layer of water 1 millimeter deep.

Significance and Applications

• Meteorology: Crucial for weather forecasting, monitoring precipitation patterns, and assessing the intensity of rainfall events.
• Hydrology: Used in hydrological models to predict runoff, streamflow, and flood potential.
• Agriculture: Helps determine irrigation needs and assess the impact of rainfall on crop growth.
• Civil Engineering: Important for designing drainage systems, managing stormwater runoff, and preventing flooding in urban areas.

Real-World Examples

• Drizzle: Light drizzle might have an intensity of 0.1 - 0.5 mm/h.
• Moderate Rain: Moderate rainfall typically falls at a rate of 2.5 - 7.5 mm/h.
• Heavy Rain: Heavy rain can exceed 7.5 mm/h, potentially leading to localized flooding.
• Extreme Downpour: Intense thunderstorms can produce rainfall rates of 25 mm/h or even higher, posing significant flood risks.

Relationship to Other Units and Formulas

While millimeters per hour directly measures precipitation intensity, it's related to other concepts in physics and meteorology.

• Volume: The total volume of water falling on an area can be calculated using the rainfall intensity and the area:

  $Volume = Rainfall\ Intensity \times Area \times Time$

• Conversion: It's helpful to know how mm/h related to other units:

  • 1 mm/h ≈ 0.039 inches/hour
  • 1 inch/hour ≈ 25.4 mm/h

Interesting Facts and Notable Figures

While no specific "law" is directly associated with millimeters per hour, the measurement is integral to quantitative precipitation estimation (QPE) and quantitative precipitation forecasting (QPF) efforts, which are continually advancing.

Vilhelm Bjerknes: While not directly tied to mm/h itself, Bjerknes' work on weather forecasting laid the foundation for the science that utilizes this unit extensively. He was a Norwegian physicist and meteorologist who founded the Bergen School of Meteorology.