Tag Archives: drought

The High Pressure Ridge

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities and you. In this blog we’ll be discussing pressure during dry weather.

The High Pressure Ridge

In “The Rise of the Ridiculously Resilient Ridge,” the author points out that persistent high pressure in recent years led to extreme drought in California. In fact, the terminology, “Ridiculously Resilient Ridge” of atmospheric high pressure is frequently used to describe ‘the unusually persistent atmospheric anomaly responsible for redirecting winter storms over the Pacific and ultimately bringing record-breaking warmth and dryness to the Golden State.” But what amount of high pressure is occurring?

As shown in the figure below, a pressure of 45 mb above the middle atmospheric pressure (500mb geopotential height (GPH)) is attributed to be the cause of unusually persistent weather patterns. This level deflects storms that would bring rain and snow to ease drought conditions. With 1 bar = 1000 mb at sea level, 500  mb is near 5,500 meters (18,000 ft).

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The middle atmospheric pressure (500 mb geopotential height) anomaly (meters) for the Ridiculously Resilient Ridge, Oct-May 2012-2015. Source: The Rise of the Ridiculously Resilient Ridge

In contrast to the ridge that tends to bring warmer and drier weather, a trough is a lower pressure region that tends to bring in cooler and cloudier weather as it approaches. Both are analyzed on pressure surfaces aloft such as 850, 700, 500 and 300 mb.

In July 2016, according to the National Oceanic and Atmospheric Administration, a “heat dome” occurred over large portions of the United States. The websites states that “a heat dome occurs when high pressure in the upper atmosphere acts as a lid, preventing hot air from escaping.” This atmospheric occurrence forces air to sink back to the surface, warming the air even further on its way down.

The heat dome that resulted from the high pressure prompted the National Weather Service to issue heat alerts for more than a dozen states across the U.S.

What do you think/Comments?
Do you have a pressure sensing question? Let me know and I’ll address it in an upcoming blog.
-Han Mai, Senior Marketing Specialist, All Sensors Corporation (hmai@allsensors.com)

The Pressure for Fresh Water

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities and you. In this blog we’ll be discussing the role pressure plays in the desalination efforts in California.

The Pressure for Fresh Water

With water shortages occurring in all regions of the world and especially in California, new sources of water are being explored.  In some cases, the new source uses an old approach. Desalination of sea water is getting new attention after being shelved for decades in Santa Barbara. Also, San Diego is building the nation’s largest ocean desalination plant that will be completed in 2016. Pressure is an integral part of turning sea water into drinkable/usable water.

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Courtesy Bay Area News Group

A reverse osmosis (RO) process is used to separate the dissolved salts in a saline solution by flowing the liquid through a water-permeable, pressure-driven membrane. The pressure required depends on the type of membrane and the desalination being performed. For example, the desalination plant on Catalina Island uses 900 psi to treat ocean water. Treating underground brackish water only requires 200 to 300 psi.

As shown in the table, there are four categories or classes of pressure-driven membranes for desalination.

 Membrane Type Pore Size Transmembrane Pressure Application 
Microfiltration (MF) 0.1 – 3 micron 1- 30 psi Turbidity reduction and bacteria removal
Ultrafiltration (UF) 0.01-0.1 micron 1- 30 psi Same as MF as well as removing viruses and some color, odor and organics
Nanofiltration (NF) < 0.002 micron 75- 150 psi Natural organic matter (NOM) removal
Reverse osmosis (RO) non-porous 150-500 psi Removing monovalent salt

MF/UF membranes are being increasingly employed in the desalination process to shield other membrane types from suspended solids and larger colloidal material that are detrimental to their performance. As part of the control and monitoring process, the differential pressure is sensed across the membrane at each phase.

What do you think/Comments?
Do you have a pressure sensing question? Let me know and I’ll address it in an upcoming blog.
-Han Mai, Senior Marketing Specialist, All Sensors Corporation (hmai@allsensors.com)

Pressure Sensors’ Role in Solving Drought Problems

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities and you. In this blog we’ll discuss the importance of pressure sensors’ role in solving drought problems.

Pressure Sensors’ Role in Solving Drought Problems

Sensors play an essential role in preventing excessive water usage and reducing water consumption to minimize the impact of drought situations. Of course there are many actions to conserve water that users can implement that do not involve sensors, but sensors can:

  • Determine if crop irrigation is sufficient to prevent over watering – soil monitoring through rain, temperature, wind, moisture sensors and more.
  • Detect leaks to avoid unnecessary water usage.

Pressure determines the flow rate and consequently the amount of water that is consumed so reducing the water pressure is a common conservation recommendation. Pressure regulators have a built-in pressure sensing mechanism.

Leak Detection

A common technique to determine if a system has leaks has three steps: pressurize the system, isolate the system from the pressure source and then measure the pressure to determine if a pressure drop occurs within a given amount of time. For residential and commercial water users, this would mean adding a pressure sensor to a system that already can measure unnecessary flow.

The utility’s water meter can identify water consumption with its low-flow indicator. Water flow when all water usage is turned off indicates leaking faucets, toilets, irrigation valves or even leaky pipes. Some estimates blame undetected water leaks for 5 to 15% of a private residence’s water consumption.

With today’s wireless technology and sophisticated computing capabilities, pressure sensing could become a tool for utilities to monitor their distribution networks to detect and identify the location of leaks before they become obvious geysers and floods. Researchers in Barcelona, Spain have been investigating this distributed pressure sensing approach for several years.  Using the proper number of appropriately placed pressure sensors in the distribution network generates a leakage signature that allows leakage localization. The leakage detection procedure compares real pressure and flow data with estimates using a simulation of the mathematical network model.  Genetic Algorithms allow the system to generate solutions to leakage problems in a much shorter timeframe than existing approaches.

With water conservation becoming more and more of an issue, both users and suppliers need to take the appropriate steps to ensure future availability. Pressure sensors could be a major part of the solution.

What do you think/Comments?
Do you have a pressure sensing question? Let me know and I’ll address it in an upcoming blog.
-Dan DeFalco, Marketing Manager, All Sensors Corporation (ddefalco@allsensors.com)