Good Evening good people passing by zoomradar. And to my good Colleague Jeff Beradelli that best MET I know. I know its been awhile since my last educational weather blog insert but I have been busy with school. Anyway I am here to blog about different weather environments called barotropic and baroclinic weather systems and where these two environments are situated.
In this Blog insertion I will discuss the definition of Barotropic and Baroclinic.
I will begin with the Barotropic Model:
The root word of Barotropic is tropic. So logic would say it must be a tropical climate or tropical weather conditions. If you guessed that you are right. barotropic is a tropical climate or situated in the tropics most of the year or in the sub-tropics in the summer as well. Barometric Pressure – Surfaces of constant pressure coincide or running parallel with surfaces of constant density and temperature. Temperatures – Temperatures in a Barotropic environment are homogenous and uniform. Warm and humid throughout the year with little fluctuation in temperature.
In a Barotropic environment in the tropics there is NO Advections such as Cold Air Advection or Warm Air Advections, No fronts such as Cold or Warm Fronts, nor any occluded fronts are present here. Like I stated before there can be a barotropic environment in the subtropics (Sub – means near or next to) which is Florida to as far North as the Southeast U.S. and/or even in the mid-latitudes at times during the summer. The Atmospheric Structure – is uniform, Winds are unidirectional and increasing with height, NO THERMAL ADVECTIONS.
I want to thank nptel.ac.in for this graphic. This is textbook Barotropic Model of constant fluid pressure throughout the atmosphere.
2. BAROCLINIC –
I will concentrate most of the blog on BAROCLINICITY because this environment affects most of us in the United States most of the time in most seasons.
A. Mid – Latitudes = Surfaces of constant pressure intersect surfaces of constant density(temperature). Surface lines cross pressure lines.
B. Temperatures – Temperatures in a baroclinic environment are heterogenous – which means large temperature differentials.
There are temperature advections warm and cold advections, there are many fronts here warm, cold and occluded, the Polar Jetstream is located here as well as Low Pressure Troughs and High Pressure Ridges.
C. Atmospheric Structure – In a Baroclinic environment the upper levels 500mb and above are characterized by large WAVES – Ridges and Troughs. Primarily the Polar Jetstream governs the troughs and Ridges. For example, if there is a DIP in the Jetstream in the Eastern United States there will be a Low Pressure Trough in the East and a High Pressure Ridge in the Western United States. As the Jetstream LIFTS a High Pressure Ridge moves in. I will put a graphic to this so its easy to understand.
Low Levels in a baroclinic environment exhibit closed low pressure cells and WEAKER height and vorticity gradients(spin). Furthermore, low pressure at the surface is a closed system, so isobars( lines on a weather map that display equal pressure) around it are closed or circular. So at low levels isolated minimum pressure are less wave like as in upper level and more cellular and less fluid than upper levels.
D. Winds – In a baroclinic environment Wind Speeds INCREASE with height up to the tropopause(50 – 65K feet) due to the baroclinic nature of the atmosphere in the mid-latitudes. Furthermore as you travel poleward there is a DECREASE in temperature thus the thermal wind is evident and sets up. I can get complicated here but I will break this down so its easy to understand. The THERMAL WIND – This is just a pressure gradient and a temperature gradient in the mid to upper levels 500mb and up. It is essentially the difference in temperature between the Poles and the tropics. The Cold environment has a thinner atmosphere thus the stratosphere is closer to the surface and The Warm Environment has a thicker atmosphere thus the tropopause and the stratosphere is much higher in the tropics than the poles. The thicker the atmosphere – expand the atmosphere or stretch it you expand the Pressure gradient force from WARM TO COLD, Coriolis Force pushes cold air to the left thus the creation of the Jetstream. The JETSTREAM – is a stream like a river in the upper atmosphere of very strong winds, the Jetstream separates the cold air from the warm air in the mid latitudes.
Here is a perfect baroclinic environment. In the upper levels strong Jetstream showing divergence which promotes the birth of Low Pressure and at the surface cold air advection in correspondence with a DIP in the Jetstream signifies an upper trough and Warm air advection under the High Pressure ridge or in the warm sector. Remember this DIP in the Jetstream = trough. LIFT = Ridge. Source tornado.sfsu.edu This graphic clearly shows baroclinic instability. warm at the surface and cold aloft.
Before I get to the second part of this blog next week that discusses Models and Systems of Barotropic and Baroclinic environments, I wanted to touch upon meteorologists roll in tracking disturbances.
3. TRACKING DISTURBANCES
These can contain weak troughs or weak low pressure, weak ridges or weak high pressure. Conversely strong troughs and strong ridges as well are found here in the Baroclinic Flow.
A. Weather Forecasters – forecasters customarily focus on the wind and geopotential height patterns(lower the heights lower the pressure, higher the heights higher the pressure) at the surface and MOST IMPORTANT at 500mb(18000 feet) diagnose the movement and intensification of disturbances. These are all baroclinic flows – advections, troughs, ridges, etc. Also I want to note, I did a blog a little ways back on numerical weather prediction or computer model forecasts and how forecasters are relying a great deal on them. I understand that computer modelling is getting more accurate but the 500mb map is crucial and essential for providing accurate forecasts to the public.
OK next week I am going to get into Modeling and Systems of a Barotropic and Baroclinic Nature. I hoped you enjoyed this blog and if you have any questions just ask me in the comment section