Four o’clock rain, or “thunderstorm of the night”, is a weather phenomenon that occurs in the Mojave Desert in the United States. The name stems from the fact that it usually occurs around 4 pm in the afternoon, although thunderstorms can occur anytime throughout the day.
It is created when a cold low-pressure trough over the desert grinds against warm, high-pressure air coming up from the Gulf of California, creating massive thunderstorms. During the rain, temperatures drop 20 to 25 degrees and rapid rain, eerie thunder, and crackling lightning occur in a matter of minutes.
The rain normally only lasts anywhere from 15 to 30 minutes and is usually considerably light. Despite the short duration, the effects of the cool air, thunder, and lightning all make the experience unique and memorable.
What is called convectional rain?
Convectional rain is a type of rainfall that occurs when the Earth’s atmosphere becomes extremely unstable. This instability is usually caused by a combination of intense solar radiation and warm temperatures, which create a layer of warm, moist air near the ground.
As the moist air rises, it cools and condenses, forming clouds and eventually precipitation. Convectional rains are especially common in tropical and subtropical regions, and they often produce heavy rainfall.
The process of convection is also responsible for thunderstorms and other forms of intense weather. Depending on the environment, convectional rain can vary in intensity, from a light sprinkle to a sudden downpour.
The type of rain can also vary from a steady, prolonged precipitation to a short but intense thunderstorm.
How does Convectional rain occur?
Convective rain occurs when warm, moist air is lifted into the atmosphere due to convection. Convection is the process by which heat is transferred by the movement of a fluid like air or water. Warm air rises because it is less dense than cooler air.
As this warm air rises, it cools and condensation forms. The condensation forms clouds and when enough warm, moist air rises, rain droplets form and the precipitation that falls to the ground is known as convective rain.
The warmer the air, the more moisture it can hold, so convective rain is often more intense than other types of precipitation. Convective rain can occur in both the warm and cold seasons. In the warm season, convective rain is often associated with thunderstorms.
These storms form when large updrafts within the atmosphere cause warm air to rapidly rise, cool and condense, releasing energy in the form of thunder and lightning. In cold seasons, convective rain is associated with frontal systems which often bring heavy rains and sometimes snow.
Is weather an example of convection?
Yes, weather is an example of convection. Convection describes the process by which warm air rises, cool air settles, and the exchange of heat between different bodies of air takes place. On Earth, one of the most prominent examples of convection is in the atmosphere during our weather patterns.
As warm air rises, cool air will settle. This change of temperature creates the movement of air masses, leading to the development of storms, temperature changes, fronts, and other weather patterns on the planet.
The different types of convection that take place in the atmosphere include radiational cooling, adiabatic cooling, and frontal boundary lifting. All of these processes are paramount to the weather patterns we observe on Earth.
Is convectional rainfall common in summer or winter?
Convectional rainfall is most common during the summer months when the air is warmer. This is because warm air rises and leaves an area of low pressure then moisture and clouds quickly move in and form thunderstorms when cold air collides with warm air.
Convective rainfall is usually less common during the winter months as the air is usually cooler and the atmosphere tends to be more stable. In the winter, other types of precipitation become more common such as snow and sleet, which result from mixed air masses that move across the region.
What are the different types of rain?
There are four main types of rain: convective rain, orographic rain, frontal rain, and cyclonic rain.
Convective rain occurs when warm, moist air rises and cools below the dew point, causing the moisture to condense and fall as rain. This type of rain is common in tropical regions and is typically associated with thunder and lightning.
Orographic rain occurs when the wind blows moist air up the side of a mountain or hill. As the moist air moves up the mountain, it cools and the moisture condenses, causing it to fall as rain on the windward side of the mountain.
This type of rain is common in mountainous regions and is often referred to as “rain shadow” because on the leeward side of the mountain there is often very little rainfall.
Frontal rain is caused by the interaction of two different air masses, typically one warm and one cold. As the warm air rises over the cold air, the moisture condenses and falls as rain. The type of rain produced by this interaction varies depending on the temperature, humidity, and instability of the air masses.
Cyclonic rain occurs when moist air is forced upward by the pressure of a low-pressure system. As the air moves up and cools, the moisture condenses and falls as rain. This type of rain is common in areas of the world where low-pressure systems persist, such as the Gulf of Mexico, the Atlantic Ocean, and the Caribbean Sea.
How many types of rain are there?
There are five main types of rain:
1. Convective Rain: These are intense rain showers that are usually the result of warm, moist air rising rapidly and forming cumulonimbus clouds. They often occur on hot summer days, and can produce heavy downpours with thunder and lightning.
2. Orographic Rain: This is rain caused by humid air rising as it meets a mountain or hill. The air cools, and as it cools, the water vapor condenses, leading to precipitation.
3. Stratiform Rain: This is a light and steady precipitation typically associated with large clouds (stratus formations) such as those that can be seen prior to a frontal boundary.
4. Cyclonic Rain: These are showers or storms that form in a cyclone or low pressure system. They can produce moderate to heavy precipitation over a period of several hours.
5. Frontal Rain: This type of precipitation is associated with cold fronts. As a cold front approaches the warm, moist air is pushed up, condenses and forms precipitation. It is usually accompanied by gusty winds and lightning.
What is the smell of the rain called?
The smell of the rain is known as ‘petrichor’, which comes from the Greek words, ‘petros’ meaning ‘stone’, and ‘ichor’ which refers to the blood of the gods in Greek mythology. Petrichor is caused by a combination of sunlight, moisture and certain compounds called geosmin and squalene which are released from the soil into the air.
The smell is strongest after a prolonged dry spell, which is when the soil is most likely to release these compounds. It’s a pleasant yet subtle earthy, musty scent that can take you back to childhood memories of running around in the rain without a care in the world.
What is the name for rain that doesn’t hit the ground?
The name for rain that doesn’t hit the ground is virga. Virga is a term used to describe precipitation in the form of liquid or ice that falls from the clouds but doesn’t reach the ground. While most of the liquid or ice evaporates before it reaches the ground, sometimes it does reach the ground as light showers or snow.
Virga is often seen during fair weather, but can also form during storms. Through the process of evaporative cooling, virga can cause the temperature to drop and winds to increase.
How is rainfall classified?
Rainfall is classified according to intensity and also by volume. Intensity refers to the amount, usually measured in millimeters (mm) of rain that falls within a short amount of time, usually within a period no longer than an hour.
Intensity is usually categorized into light, moderate, or heavy. A light rain is when the intensity ranges below 2. 5 mm per hour, moderate rain is between 2. 5 mm to 7. 6 mm per hour, and heavy rain is when the intensity exceeds 7.
6 mm per hour.
Volume, on the other hand, refers to the total amount of rainfall, usually measured in millimeters, that fell over a period of time such as a day, a month or a year. Volume is often classified by the total amount, with categories such as less than 100 mm, 100 to 200 mm, and greater than 200 mm.
In addition to intensity and volume, rainfall can also be classified by its type, such as convectional, orographic, or cyclonic rainfall. Convectional rainfall occurs when warm, moist air rises, forming large clouds, and eventually leads to the condensation of water droplets that fall back to the ground as rain.
Orographic rainfall is precipitation caused by air passing over mountains, which then rises and cools, resulting in condensed liquid that falls back to the ground as rain. Cyclonic rainfall is caused by rotating air around low-pressure systems, with the moist air eventually cooling and condensing into droplets that fall back to the ground as rain.
Which rainfall is called orographic or relief rainfall?
Orographic or relief rainfall is a type of precipitation that occurs when moist air is forced up and over a certain topographic feature, such as a mountain. As the air rises, it cools and condenses, releasing its moisture in the form of rain, sleet, hail, snow, or any combination of those elements.
This type of rainfall is created when a prevailing wind blows air masses up and over an obstacle, such as a mountain range. The most notable example of this is the strong, steady rains of the Pacific Northwest, which are formed when moist air from the ocean is pulled up and over the coastal mountains.
Orographic rain is particularly pronounced in mountainous areas as the moisture is quickly released at higher altitudes. It also can create areas of heavy precipitation on the windward side of the mountain, with much less precipitation on the leeward side.
Is precipitation another name for rainfall?
No, precipitation and rainfall are not the same thing. Rainfall is a type of precipitation, but precipitation does not always mean rainfall. Precipitation is the general term for water that enters the atmosphere in any form and reaches the ground, which includes the liquid form of rain, snow, sleet, and hail.
In some cases, if the temperature is high enough, the precipitation is actually a gas, such as water vapor. Precipitation is commonly measured by its depth or amount, known as its “intensity. ” Rainfall is simply water droplets that fall from the atmosphere to the Earth’s surface.