Pressure systems impact on Solar Radiation
The simple weather element of pressure can also impact the solar radiation levels of the earth. This is a very interesting aspect to think about it fits in with the topic of clouds which we just finished discussing above. So pressure first it’s important to know that we have two types of pressure low pressure and high pressure, both offer different types of weather patterns. First, low pressure, ahead of low pressure you will see the winds tend to favor a southerly component in the Northern Hemisphere, this means that warmer air is movingnorthward over a region, this warmer air is then measured by a thermometer to give us our temperatures that we feel every day, these temperatures are then recorded for history and climate purposes.
Climate is data over a 30 year average which is needed for finding the average temperature of a given location on the earth, also note that almost all temperatures that are recorded on earth are done by computer ran software that hooks into the weather stations, there are still some human recorded temperatures as well, but most of the world is now using computer driven software. So now back to the low pressure and the warmer winds and temps, if you live in a place that deals with a lot of low pressure systems moving through your region your going to see more days that have this warm feeling from the southerly flow ahead of the low pressure, giving you more warmer days than a place that doesn’t see as many low pressure warm air events. Now on the back side of this low pressure the winds in the Northern Hemisphere will change to a northerly component, this means it will now push in the colder air from the north allowing for a place to see cooler temperatures in the summer and colder temperatures in the winter.
The other pressure system is the high pressure center, here we see the exact opposite taking place such as the colder air or cooler air is on the eastern side of this high pressure, while on the western side its warm to warmer for the Northern Hemisphere.
So now knowing that, let’s look at how this impacts climate. On earth we have what are known as Semi-permanent pressure systems meaning that they remain pretty stationary not moving a lot except on a seasonal basis, this sets the stage for climate patterns over given locations. We will use the West coast of the United States for this example, during the summer months, a semi-permanent high pressure system sits over the Pacific Ocean to the west of the coast, this means the West Coast would be in the northern flow of this air, that is another reason why the weather is mostly cooler in the summer for the west coast near the water.
While, if we look at the United States Gulf Coast and Southeast, during the summer months it tends to be hot/humid over the region, the reason for this is that to the east over the Atlantic Ocean another semi-permanent high pressure establishes itself, known to many as the Bermuda-Azores high, this allows for the warm southerly flow to advance into the Gulf Coast and Southeast United States making for a hot and muggy summer in
Now, examining how these same pressure systems can impact the climate even further, to do this we need to understand a term known as the “JET STREAM” this describes the winds that are on average 20-30,000ft above the ground, this is where we find very strong winds that circulate the globe every day of the year, this is known as the Atmospheric Highway. Those two semi-permanent high pressure centers that I just mentioned above interact with these very strong winds aloft. To see how this work’s imagine a body builder, when they lift the weight off the bar or ground the weights rise to the air, now think about the warmer air found at the tropics created by the solar radiation, when it’s strong it heats up the earth, this heat in the Northern Hemisphere then goes northward, forcing those semi-permanent pressure systems to also shift northward, in return it will now alter the track of the jet-stream those very strong winds aloft, this then can lead to weather pattern changes, which in return can lead to extreme events on the earth, such as in the early 2000’s we started to see increase in drought over the Western US along with the Southern Plains, due to this warmer air getting pushed further northward and also the low pressure systems being forced further northward, not allowing for the normal amounts of rainfall to hit these regions. So as you can see when the earth goes through a warming phase we start to note more warming events to take place such as heat waves, droughts and increase in severe weather patterns such as more tornado outbreaks along with stronger hurricanes.
Now, let’s take a look at the opposite of a warming event and when a cooling event takes place, these same semi-permanent pressure systems(The body builders) now push further southward as the cold air is stronger, this again alters the jet stream patterns which now sends rainfall and snowfall patterns further south. So you now begin to see rare snowfall events in Florida and along the Gulf Coast of the United States things that don’t happen to often maybe we will call them “EXTREME EVENTS”, this is due to the shift in all of these moving parts, which can further be related back to the sun and it’s solar radiation, this leads to more cold weather events, such as longer winters, colder winters, increase in winter storms, decrease in hurricane amounts and also decrease in tornadoes. Pressure does matter in climate.