The 41-year-old Finn was appointed this week, having played for the club between 1997 and 2000.
"We have the Latin guys who have strong blood and are passionate," said Caixinha from Portugal.
"Maybe we just needed to add someone from further north who can add a little bit of ice to calm down things from time to time."
Having been chosen ahead of other former Rangers players such as Barry Ferguson, John Brown, Kevin Thomson and Alex Rae, Johansson will join Caixinha's compatriots Helder Baptista, Pedro Malta and Jose Belman.
Caixinha told RangersTV: "We had a fantastic list of candidates and it really was really a pleasure.
"We tried to fill three major points and it wasn't an easy decision.
"First of all, we wanted someone with a Rangers past. The second point was of course to know the Scottish reality of football and the third, which was also important and which makes all the difference, is to align with our dynamic, our processes and our methodologies.
"We chose Jonatan and we believe in him. He will be a good assistant to add to our team because he's a quality guy, he is a hard worker and he is clever.
"I want all of the assistants to share with me the responsibility of what it means to be managing this club."

Sir Tim Berners-Lee was speaking to the BBC following the news that he has been given the Turing Award.
It is sometimes known as the Nobel Prize of computing.
Sir Tim said moves to undermine encryption would be a "bad idea" and represent a massive security breach.
Home Secretary Amber Rudd has said there should be no safe space for terrorists to be able to communicate online. But Sir Tim said giving the authorities a key to unlock coded messages would have serious consequences.
"Now I know that if you're trying to catch terrorists it's really tempting to demand to be able to break all that encryption but if you break that encryption then guess what - so could other people and guess what - they may end up getting better at it than you are," he said.
Sir Tim also criticised moves by legislators on both sides of the Atlantic, which he sees as an assault on the privacy of web users. He attacked the UK's recent Investigatory Powers Act, which he had criticised when it went through Parliament: "The idea that all ISPs should be required to spy on citizens and hold the data for six months is appalling."
In the United States he is concerned that the principle of net neutrality, which treats all internet traffic equally, could be watered down by the Trump administration and the Federal Communications Commission.
"If the FCC does move to reduce net neutrality I will fight it as hard as I can," he vowed.
The web's creator also said he was shocked by the direction the US Congress and Senate had taken when they voted to scrap laws preventing internet service providers from selling users' data.
He said privacy online was as important as the trust between a doctor and a patient.
"We're talking about it being just a human right that my ability to communicate with people on the web, to go to websites I want without being spied on is really, really crucial."
Last month, in an open letter marking the 28th anniversary of the web, Sir Tim warned about the problem of fake news spreading online.
He repeated those concerns and said there might be a design flaw in some web services: "Fake things, false things tend to propagate more than truth and in a way maybe hatred tends to propagate in some cases more than love."
He added that everyone had a responsibility to address this issue, including the major technology companies.
"People who have created those various social networks need to sit back and look at the way they are being built," he said.
Sir Tim said it was a "massive honour" to win the Turing Award, which is given by the Association of Computing Machinery.
The prize, now in its 50th year, is widely recognised as the most prestigious in computing.
Past winners include Vint Cerf and Bob Kahn, considered the "fathers of the internet;" and the artificial intelligence pioneer John McCarthy.
The citation for Sir Tim Berners-Lee reads: "For inventing the world wide web, the first web browser, and the fundamental protocols and algorithms allowing the web to scale."
In recent years, Google has sponsored the prize which now includes a cheque for $1m (Â£803,000). That will be handed over in a ceremony marking 50 years of computing innovation in San Francisco in June.
Rangers manager Pedro Caixinha believes Jonatan Johansson will bring a cool head to the Ibrox coaching staff.
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The web's creator has attacked any UK plans to weaken encryption and promised to battle any moves by the Trump administration to weaken net neutrality.